Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$45.82	9.595%	$50.2164	$50.22	$50.20	$50.20
Purchase #2	$14.42	8.255%	$15.6104	$15.61	$15.60	$15.60
Purchase #3	$200.37	11.523%	$223.4586	$223.46	$223.45	$223.50
Purchase #4	$77.48	7.167%	$83.033	$83.03	$83.05	$83.00
Purchase #5	$83.64	8.277%	$90.5629	$90.56	$90.55	$90.60
Purchase #6	$212.90	13.648%	$241.9566	$241.96	$241.95	$242.00
Purchase #7	$158.78	5.461%	$167.451	$167.45	$167.45	$167.50
7 purchase totals =	$793.41		$872.2889	$872.29	$872.25	$872.40