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	$43.53	6.707%	$46.4496	$46.45	$46.45	$46.40
Purchase #2	$43.71	4.126%	$45.5135	$45.51	$45.50	$45.50
Purchase #3	$92.72	13.422%	$105.1649	$105.16	$105.15	$105.20
Purchase #4	$138.94	13.634%	$157.8831	$157.88	$157.90	$157.90
Purchase #5	$144.96	10.205%	$159.7532	$159.75	$159.75	$159.80
Purchase #6	$126.38	11.233%	$140.5763	$140.58	$140.60	$140.60
Purchase #7	$90.71	8.729%	$98.6281	$98.63	$98.65	$98.60
7 purchase totals =	$680.95		$753.9687	$753.96	$754.00	$754.00