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	$219.39	5.135%	$230.6557	$230.66	$230.65	$230.70
Purchase #2	$35.30	11.683%	$39.4241	$39.42	$39.40	$39.40
Purchase #3	$240.58	10.496%	$265.8313	$265.83	$265.85	$265.80
Purchase #4	$66.33	9.627%	$72.7156	$72.72	$72.70	$72.70
Purchase #5	$225.35	7.793%	$242.9115	$242.91	$242.90	$242.90
Purchase #6	$141.28	9.350%	$154.4897	$154.49	$154.50	$154.50
Purchase #7	$146.58	3.804%	$152.1559	$152.16	$152.15	$152.20
7 purchase totals =	$1,074.81		$1,158.1838	$1,158.19	$1,158.15	$1,158.20