but you're right - if a transaction is under the percentage, no tax is owed and none will be collected.

When I was a kid, baseball cards were 5 cents a pack. If we bought 2 packs, it cost 10 cents. If we bought 3 packs, it cost 16 cents. We learned to stagger our purchases to save a penny. (a penny could buy small candy or 2 pretzel rods back then)