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	$157.88	13.733%	$179.5617	$179.56	$179.55	$179.60
Purchase #2	$56.75	7.829%	$61.193	$61.19	$61.20	$61.20
Purchase #3	$224.42	10.280%	$247.4904	$247.49	$247.50	$247.50
Purchase #4	$104.99	6.221%	$111.5214	$111.52	$111.50	$111.50
Purchase #5	$114.80	8.485%	$124.5408	$124.54	$124.55	$124.50
Purchase #6	$180.53	10.631%	$199.7221	$199.72	$199.70	$199.70
Purchase #7	$215.43	9.698%	$236.3224	$236.32	$236.30	$236.30
7 purchase totals =	$1,054.80		$1,160.3518	$1,160.34	$1,160.30	$1,160.30