The tax is applies after the total is added up so there is no other choice When I was a kid a value meal at McDonalds was $3.18 after tax, but two of them was $6.37 - that extra penny over all the meals McDonalds sells in a state adds up to a lot of money and they were not going to let that go.

As long as all the amounts when taxed add up to round numbers, you don't need pennies.