Hi Taro,
If it is in foreign currency sap note 2008817 will help you. There could be some differences.
If you have withholding tax in payment and monthly accumulation active and you want to know how much tax was withheld for each invoice, you could check WITH_ITEM and REGUPW tables. In table WITH_ITEM you could check for QBSHH, QBSHB, accumulated auxiliary fields (WT_ACCWT, WT_ACCWTA) and corresponding tax base.
I had a case some time ago in which appeared difference for a tax with 80% rate for withholding in foreign currency. Other w.taxes had differences occasionally on 1 cts but the had 10% rate.
SAP rounds cents 0-4 goes down, 5-9 goes up. sapnote 1459557 talks about withholding calculations and cents for Australia. This is a way to change SAP logic.
Kind Regards