Cleaning up the receipt accruals

How do you clean up the receipt accrual account for recipt variances that build up over time? 

My client is a processing manufacturer and purchases ingredients all over the world.  About 30-40% of the PO/invoices have rounding differences for qty.  This is mainly due to the conversion of Kilos to lbs and visa versa.

Each time there is a rounding difference it remains in the accrual account.

1.  We need some kind of report to help identify these differences.

2.  Is there a way we can write off or isolate these differences up front?

Thanks in advance.

Tony