AP EDI File Header Amount & Oracle Line Calculations Totals Not Matching

We are setup with Suppliers sending us our AP invoices via EDI files.  The EDI file contains a header amount and line information (qty and unit price).  When Oracle calculates the quantity and unit prices for each line, the total of lines is not matching the header amount sent in the file.  This is causing all of these invoices to have a hold status placed.  (Usually, the amounts differ by only pennies.)

Are there any ideas on why this is happening?  Is there any way to adjust the line amounts during the import (or other) process, so the invoices don't have to be manually adjusted each day?