Things to Check if a Sale Doesn't Add Sales Tax:
1) The first thing to check is to edit the sale and make sure that each
taxable item has a "T" for Taxable on the right side of the screen.
Make sure each taxable line-item has a "T" for taxable on the
far right side next to the Extension amount. If an item is not marked
as taxable, highlight that line, press the Left-Arrow in the price field
and then pick Change Tax from the list.
2) If you have a sale which simply won't add sales tax, even if the
items do have the T, then somehow the sales tax for just that sale
might have somehow been set to zero. To fix this, edit the sale and
go to the first empty line.
When prompted for the Sku No, press the <Enter> key three times
until you have the prompt for Continue, More or Tax. Choose Tax
and then you can reset the tax rate for this sale to the correct value.
Be sure to enter it as a percentage, not a fraction (e.g. type 6.00
NOT 0.06 for 6%)