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	$59.42	3.511%	$61.5062	$61.51	$61.50	$61.50
Purchase #2	$14.51	5.817%	$15.354	$15.35	$15.35	$15.40
Purchase #3	$131.74	5.142%	$138.5141	$138.51	$138.50	$138.50
Purchase #4	$33.69	10.298%	$37.1594	$37.16	$37.15	$37.20
Purchase #5	$214.57	11.365%	$238.9559	$238.96	$238.95	$239.00
Purchase #6	$72.81	6.748%	$77.7232	$77.72	$77.70	$77.70
Purchase #7	$48.64	10.697%	$53.843	$53.84	$53.85	$53.80
7 purchase totals =	$575.38		$623.0558	$623.05	$623.00	$623.10