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	$214.89	13.308%	$243.4876	$243.49	$243.50	$243.50
Purchase #2	$82.48	11.131%	$91.6608	$91.66	$91.65	$91.70
Purchase #3	$90.96	7.130%	$97.4454	$97.45	$97.45	$97.40
Purchase #4	$188.85	13.568%	$214.4732	$214.47	$214.45	$214.50
Purchase #5	$208.89	10.155%	$230.1028	$230.10	$230.10	$230.10
Purchase #6	$99.50	11.676%	$111.1176	$111.12	$111.10	$111.10
Purchase #7	$150.90	5.247%	$158.8177	$158.82	$158.80	$158.80
7 purchase totals =	$1,036.47		$1,147.1051	$1,147.11	$1,147.05	$1,147.10