Hi Akbar,
Ignore my previous suggestion which is not applicable for APP.
The correct sequence is first you have to define the rounding unit for your currency in OB90 for example you can give 100 there.
Next you have to change the vendor master in FK02 and activate Individual payment so that each line item will be settled individually.
I will explain the difference with example.
lets assume for a vendor there is two open items of 99.6 and 99.7.
If you activated individual line item he will be paid 100 for both cases so 200 will be paid.
If you havent activated he will be paid 199(99.6+99.7=199.3 rounded to 199).
Hope it is clear.
Regards,
G.Sethuraman