You can use Tax Summary on the Purchase or Sales menu to change the sales tax for the entire transaction on an invoice or bill. Or, use Tax Summary For Line to change the tax reported for a single line of the transaction.
If you are making a purchase, you may need to change the sales taxes when your vendor uses a different method of rounding off than Sage 50 Accounting. As well, you may need this option for a sale if your point-of-sale or other system rounds differently.
Find the keyboard shortcuts to show tax summaries in transactions