Update Tax percentage on the invoice lines and detail

Hi All

I have 13 invoices that where loaded with the wrong tax percentage in the conversion.  These invoices should have been loaded with 6.75 percent but was loaded with 7.75%.  The amount on the invoices is correct and the invoices have been paid. the client is wanting to correct these invoices for reporting purposes to the state.  Would you happen to have some insight of what all i need to update for all the items on the invoice to show the correct amount?  i updated the lines on the invoice and they look correct but the tax details still show the