How do we avoid invoice rounding errors for multiple ship confirmed lines for the same item?

A client uses DSI and a hand-held scanner for P4205 to ship confirm multiple lot codes of the same item number. For each scan, the system multiplies the quantity shipped by the unit cost (up to four decimals) to calculate the extended amount, which is stored with only two decimals.

The client’s customer wants to see only one line on the invoice for each item number. So when the R42565 invoice print program calculates the totals for the lines that are confirmed, rounding errors occur. In the example below, the invoice amount will be off by one cent for that item number. The correct price on the invoice line for the summarized item should be $661.11, but the R42565 will print $661.12.