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	$89.42	4.190%	$93.1667	$93.17	$93.15	$93.20
Purchase #2	$90.90	4.588%	$95.0705	$95.07	$95.05	$95.10
Purchase #3	$180.54	5.145%	$189.8288	$189.83	$189.85	$189.80
Purchase #4	$106.67	10.540%	$117.913	$117.91	$117.90	$117.90
Purchase #5	$166.73	5.302%	$175.57	$175.57	$175.55	$175.60
Purchase #6	$128.37	13.858%	$146.1595	$146.16	$146.15	$146.20
Purchase #7	$204.55	12.300%	$229.7097	$229.71	$229.70	$229.70
7 purchase totals =	$967.18		$1,047.4182	$1,047.42	$1,047.35	$1,047.50