One way to think about radians is "feet (of perimeter) per feet (of radius)" -- the dimensional units cancel and you're left with a dimensionless unit.
Taxes are a familiar dimensionless unit -- dollar owed to the government, per dollar spent on snacks. The dollars cancel and you're left with a raw percentage. (actually, to convert to a percentage you multiply by 100 percent per whole; another dimensionless conversion)
If they are truly dimensionless, when is it meaningful to multiply a non-currency value by them? There’s still a semantic that attaches the rate to dollars obtained in a transaction.
Taxes are a familiar dimensionless unit -- dollar owed to the government, per dollar spent on snacks. The dollars cancel and you're left with a raw percentage. (actually, to convert to a percentage you multiply by 100 percent per whole; another dimensionless conversion)