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	$245.82	3.533%	$254.5048	$254.50	$254.50	$254.50
Purchase #2	$34.26	10.486%	$37.8525	$37.85	$37.85	$37.90
Purchase #3	$145.75	13.604%	$165.5778	$165.58	$165.60	$165.60
Purchase #4	$208.31	4.555%	$217.7985	$217.80	$217.80	$217.80
Purchase #5	$116.76	10.580%	$129.1132	$129.11	$129.10	$129.10
Purchase #6	$48.37	8.376%	$52.4215	$52.42	$52.40	$52.40
Purchase #7	$235.43	7.797%	$253.7865	$253.79	$253.80	$253.80
7 purchase totals =	$1,034.70		$1,111.0548	$1,111.05	$1,111.05	$1,111.10