Payables Open Invoices Interface: Temp Amount Mismatch When Imported with Tax Lines

We're on release 12.0.6.  My question involves Tax lines with a tax amount on the imported AP invoice.

Our imported AP invoice is imported with a Tax line with a valid Oracle tax code.  It's a 'generic' tax code that we created with a zero percentage or 0%.  We're using this, because the tax amount is actually calculated in an external system (the source of the imported AP invoice).  That pre-determined tax amount from the source system is the value in the AMOUNT column of the Tax line on the  AP_INVOICE_LINES_INTERFACE  table.  The imported Tax line also has a number in the TAX_RATE column that represents the rate used in the source system; we do not want or expect Oracle to use this rate in any calculation.