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	$101.70	9.461%	$111.3218	$111.32	$111.30	$111.30
Purchase #2	$59.70	11.620%	$66.6371	$66.64	$66.65	$66.60
Purchase #3	$155.47	12.271%	$174.5477	$174.55	$174.55	$174.50
Purchase #4	$68.64	9.538%	$75.1869	$75.19	$75.20	$75.20
Purchase #5	$55.87	10.502%	$61.7375	$61.74	$61.75	$61.70
Purchase #6	$215.41	10.819%	$238.7152	$238.72	$238.70	$238.70
Purchase #7	$141.82	3.192%	$146.3469	$146.35	$146.35	$146.30
7 purchase totals =	$798.61		$874.4931	$874.51	$874.50	$874.30