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	$59.27	5.378%	$62.4575	$62.46	$62.45	$62.50
Purchase #2	$62.49	8.289%	$67.6698	$67.67	$67.65	$67.70
Purchase #3	$117.25	12.362%	$131.7444	$131.74	$131.75	$131.70
Purchase #4	$129.63	6.105%	$137.5439	$137.54	$137.55	$137.50
Purchase #5	$44.70	3.198%	$46.1295	$46.13	$46.15	$46.10
Purchase #6	$69.75	3.333%	$72.0748	$72.07	$72.05	$72.10
Purchase #7	$26.86	13.335%	$30.4418	$30.44	$30.45	$30.40
7 purchase totals =	$509.95		$548.0617	$548.05	$548.05	$548.00