VMA : Why doesn't automation rule 05 invoke Voucher Variance?

Rule 05 :  Match to Invoice Line to Purchase Order Line to Multiple Receipt Lines, Rounding Tolerance Applied (UBE R4304020) Each invoice line received from the supplier will be matched to a single purchase order line and to the total of one or more receipt lines for the purchase order. The amount of the invoice line and the purchase order line can be
different based on allowed rounding tolerance limits. When you specify Automation Rule 05, the system matches using UBE R4304020.

We entered a supplier invoice with value more than PO and Purchase Receipt, but within Rounding tolerance. We chose to use VMA in 'Suggestion' mode. The report confirmed the matching. However, final voucher was creating ignoring the rounding off difference. For example, PO value is $20000, Purchase Receipt value is $20000, Supplier Invoice is for $20000.05. Rounding Tolerance set through P43221 is + / - 0.10