Expense Report Line Tax Rate Updates during Audit not used by AP Tax Calculation

My company does not use multi currency in any module.  For Expense Reports, users must enter the expense lines in the Ledger currency.

There is a LOV on the expense line details page where a user can mark an out of country expense as Tax Exempt (Overriding the AUS Standard 10% as defined on the expense report template).

These expense reports are submitted and approved, and receipts are required to be attached.

The AP team, using Internet Expense Audit, compares the user entered transaction to the receipt.

If the user did not change the tax rate from 10% to 0, the business process is for the auditor to update the tax code rather than send the report back to the user and require a second round of approvals.