I have been wondering why OpenERP showing wrong subtotal amount and hence the base amount for tax calculation where the taxes are included in price. Please have a look on the data:

Unit Price: 250
Qty: 20
Tax: 13.5% (included in price)
Subtotal: 4405.29, where it should be 4325

This difference increases as the quantity increases and the correct amount deviates hugely to what it should be. Anyone who went through such issue, please help.