Why the rounding rule of good receipt for local currency is different to different purchasing orders ?

Hi Gurus:

The rounding rule of good receipt for local currency in PO1 is always round up while the reaction in PO2 is commercial. Why the rounding rule between PO1 and PO2 is different ?

Processing steps of PO1 were:

1. 1. I created PO1 with 5.7 USD net price, price unit=1000 EA, quantity=10000 EA.
2. 2. Some properties belong to PO1 are: item category=S, account assignment category=X, condition type=PB00, without tax or other conditions, document currency =USD, local currency =TWD, exchange rate: 1USD= 31.4905 TWD.
3. 3. 1^st partial GR(quantity=3000): USD amount=17.10(5.7 x 3000/1000),TWD amount= 539(17.10 x 31.4905=538.48755, but SAP ERP rounded it to 539, using the rule of round up).
4. 4. I did Invoice receipt against 1^st partial GR of PO1, the TWD amount of vendor line item=538(17.10 x 31.4905=538.48755, then SAP ERP rounded it to 538, using the rule of commercial).
5. 5. Due to the difference between GR and IR, SAP created 1 TWD dollar in credit account. All of the line items are:

TWD line items for PO1 GR1 :

Debit:        Expenditure  539 TWD

  Credit:          GR/IR clearing 539 TWD

TWD line items against the GR1 above :

Debit:        GR/IR clearing  539 TWD

  Credit:               vendor 538 TWD

                       Expenditure   1 TWD

1. 6. Next did 2^nd partial GR(quantity=7000): USD amount=39.90(5.7 x 7000/1000),TWD amount= 1257(39.90 x 31.4905=1256.47095, but SAP ERP rounded it to 1257, using the rule of round up).
2. 7. Then I did Invoice receipt against 2^nd partial GR of PO1, the TWD amount of vendor line item=1256(39.90 x 31.4905=1256.47095, then SAP ERP rounded it to 1256, using the rule of commercial).
3. 8. Due to the difference between GR and IR, SAP created 1 TWD dollar in credit account. All of the line items are:

TWD line items for PO1 GR2 :

Debit: Expenditure  TWD 1257

  Credit:          GR/IR clearing  TWD 1257

TWD line items against the GR2 above :

Debit:        GR/IR clearing  TWD 1257

  Credit:               vendor      TWD 1256

                       Expenditure  TWD  1

Processing steps of PO2 were:

1. 1. I created PO2 with 8.9 USD net price, price unit=1000 EA, quantity=20000 EA.
2. 2. Some properties belong to PO2 are the same as PO1 mentioned above.
3. 3. 1^st partial GR(quantity=1247): USD amount=11.10(8.9 x 1247/1000=11.0983, SAP ERP rounded it to 11.10, using the rule of commercial),TWD amount= 349(11.0983 x 31.4905=349.4910, but SAP ERP rounded it to 349, using the rule of commercial).
4. 4. I did Invoice receipt against 1^st partial GR of PO2, the TWD amount of vendor line item=350(11.10 x 31.4905=349.54, then SAP ERP rounded it to 350, using the rule of commercial)
5. 5. Due to the difference between GR and IR, SAP created 1 TWD dollar in credit account. All of the line items are:

TWD line items for PO2 GR1 :

Debit:        Expenditure   349 TWD

  Credit:          GR/IR clearing  349 TWD

TWD line items against the GR1 above :

Debit:        GR/IR clearing  349 TWD

             Expenditure      1 TWD

  Credit:               vendor      350 TWD

1. 6. Next did 2^nd partial GR(quantity= 18753): USD amount=166.90(8.9 x 18753/1000=166.9017, SAP ERP rounded it to 166.90, using the rule of commercial),TWD amount= 5256(166.90 x 31.4905=5255.76, but SAP ERP rounded it to 5256, using the rule of commercial).
2. 7. Then I did Invoice receipt against 2^nd partial GR of PO2, the TWD amount of vendor line item=5256(166.90 x 31.4905=5255.76, but SAP ERP rounded it to 5256, using the rule of commercial)
3. 8. There is no difference between GR and IR. All of the line items are:

TWD line items for PO2 GR2 :

Debit: Expenditure  5256 TWD

  Credit:          GR/IR clearing  5256 TWD

TWD line items against the GR2 above :

Debit:        GR/IR clearing  5256 TWD

  Credit:               vendor      5256 TWD

So we can find that the rounding rule of good receipt for local currency in PO1 is always round up while the reaction in PO2 is commercial. The rounding rule to invoice receipt in both POs are the same(the rule of commercial).

Why the rounding rule between PO1 and PO2 is different ?

I am appreciated if you can propose solutions for this.

  Weaver.