Why budget check does not work with account assigment distrib. by quantity?

Question

Hi Gurus,
I have an issue in the budget check for Purchase Order (PO).
I'm using the FM B31I_ACC_PURCHASE_ORDER_CHECK.
The case is next:
1 Item with 21 account assignment type AS and distribution by quantity:
ASSET_NO QUANTITY
1           1
2           1
3           1
4           1
5           1
6           1
7           1
8           1
9           1
10          1
11          1
12          1
13          1
14          1
15          1
16          1
17          1
18          1
19          1
20          1
21          1
All account assignment are for the same G/L account, fund, functional area...
The price for each item is $2,499.14, then total price is $52,481.94 (2,499.14 * 21).
I debugged the FM B31I_ACC_PURCHASE_ORDER_CHECK and found that in FM BBP_PD_COMMITMENT_FILL_BAPI it's making a rounding with percentage:
The system assume next:
Each item is 4.76% of total (result of divide 100% / 21 = 4.76190476...) but the percentage is rounded to 2 decimals.
Then it makes the conversion by the amount corresponding to each item:
($52,481.94 * 4.76) / 100 = $2,498.1403
Finally the budget is checked by $52,460.95 (2498.1403 * 21).
But available budget is $52,481.90, the check pass, but really there are 4 cents missing (total price is $52,481.94).
Can somebody say to me if this is a standard behavior?
It can be fixed with configuration?
The problem is for multiple account assignment with distribution by quantity and:
(100 / quantity) = not integer (or have more than 2 decimals)
For example: with quantity 20 it works because 100% / 20 = 5.00%, then the budget is check exactly.

Answer 1

1503317 - System Behavior for Account Distribution between SRM and R/3 system
When using distribution by Value in a SRM document this value is not correct and a rounding occurs once this document is transferred to ERP system.
Cause
It is not possible transfer documents to the back end system with distribution by value, due to a back end restriction.
Resolution
The following information is the system behavior in R/3 / ERP:
in R/3, there is accounting distribution only by quantity or percentage. So when distribution by value is used, a rounding will always take place.
in R/3, the use of value based distribution in SRM will lead to rounding differences.
Distribution by quantity is allowed in SRM and MM side. However MM do not accept is distribution by value. This is internally converted to distribution percentage based.
Keywords
Distribution by Quantity, Distribution by Percentage, Distribution by Value