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	$205.87	13.314%	$233.2795	$233.28	$233.30	$233.30
Purchase #2	$137.72	7.625%	$148.2212	$148.22	$148.20	$148.20
Purchase #3	$43.79	6.150%	$46.4831	$46.48	$46.50	$46.50
Purchase #4	$145.85	13.245%	$165.1678	$165.17	$165.15	$165.20
Purchase #5	$116.80	6.439%	$124.3208	$124.32	$124.30	$124.30
Purchase #6	$104.66	3.560%	$108.3859	$108.39	$108.40	$108.40
Purchase #7	$137.57	9.819%	$151.078	$151.08	$151.10	$151.10
7 purchase totals =	$892.26		$976.9363	$976.94	$976.95	$977.00