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	$185.39	6.216%	$196.9138	$196.91	$196.90	$196.90
Purchase #2	$214.85	6.160%	$228.0848	$228.08	$228.10	$228.10
Purchase #3	$175.95	13.593%	$199.8669	$199.87	$199.85	$199.90
Purchase #4	$231.45	4.658%	$242.2309	$242.23	$242.25	$242.20
Purchase #5	$111.32	10.634%	$123.1578	$123.16	$123.15	$123.20
Purchase #6	$193.42	5.826%	$204.6886	$204.69	$204.70	$204.70
Purchase #7	$235.73	12.653%	$265.5569	$265.56	$265.55	$265.60
7 purchase totals =	$1,348.11		$1,460.4997	$1,460.50	$1,460.50	$1,460.60