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	$244.67	4.685%	$256.1328	$256.13	$256.15	$256.10
Purchase #2	$48.50	7.819%	$52.2922	$52.29	$52.30	$52.30
Purchase #3	$118.93	10.791%	$131.7637	$131.76	$131.75	$131.80
Purchase #4	$49.99	13.744%	$56.8606	$56.86	$56.85	$56.90
Purchase #5	$34.77	7.224%	$37.2818	$37.28	$37.30	$37.30
Purchase #6	$110.48	12.697%	$124.5076	$124.51	$124.50	$124.50
Purchase #7	$53.27	4.543%	$55.6901	$55.69	$55.70	$55.70
7 purchase totals =	$660.61		$714.5288	$714.52	$714.55	$714.60