Adding Sales Tax To Transaction Codes Merged

We have sales tax but only for retail not services. As far as I can tell the only thing you can automatically add sales tax to is tuition (not something we need to do). So I'd love the ability to checkbox a specific transaction code ie: "Retail" or "Costumes" etc with an automatic sales tax. I'm not allowed to just include it in the price, it has to be a separated out.