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	$118.29	7.490%	$127.1499	$127.15	$127.15	$127.10
Purchase #2	$166.53	3.719%	$172.7233	$172.72	$172.70	$172.70
Purchase #3	$94.90	11.308%	$105.6313	$105.63	$105.65	$105.60
Purchase #4	$44.92	7.111%	$48.1143	$48.11	$48.10	$48.10
Purchase #5	$146.27	8.178%	$158.232	$158.23	$158.25	$158.20
Purchase #6	$236.57	3.201%	$244.1426	$244.14	$244.15	$244.10
Purchase #7	$235.89	13.315%	$267.2988	$267.30	$267.30	$267.30
7 purchase totals =	$1,043.37		$1,123.2922	$1,123.28	$1,123.30	$1,123.10