The third tab at the bottom of the screen allows you to assign a tax to each item.

If items have different taxes, on this screen each item will be assigned its corresponding: sales tax, take-away tax (this tax is typically applied in hospitality businesses), and purchase tax.
You can multiselect, to add the tax to several items at the same time, without having to select them one by one.

Hiopos allows adding more than one tax to items, allowing them to be accumulated or not.