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	$69.28	10.346%	$76.4477	$76.45	$76.45	$76.40
Purchase #2	$173.58	13.224%	$196.5342	$196.53	$196.55	$196.50
Purchase #3	$148.38	7.226%	$159.1019	$159.10	$159.10	$159.10
Purchase #4	$208.30	6.595%	$222.0374	$222.04	$222.05	$222.00
Purchase #5	$68.96	6.176%	$73.219	$73.22	$73.20	$73.20
Purchase #6	$55.82	11.672%	$62.3353	$62.34	$62.35	$62.30
Purchase #7	$136.27	13.336%	$154.443	$154.44	$154.45	$154.40
7 purchase totals =	$860.59		$944.1185	$944.12	$944.15	$943.90