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	$172.60	13.732%	$196.3014	$196.30	$196.30	$196.30
Purchase #2	$176.61	10.477%	$195.1134	$195.11	$195.10	$195.10
Purchase #3	$162.49	8.171%	$175.7671	$175.77	$175.75	$175.80
Purchase #4	$79.66	13.726%	$90.5941	$90.59	$90.60	$90.60
Purchase #5	$157.38	5.275%	$165.6818	$165.68	$165.70	$165.70
Purchase #6	$12.64	3.684%	$13.1057	$13.11	$13.10	$13.10
Purchase #7	$113.28	4.363%	$118.2224	$118.22	$118.20	$118.20
7 purchase totals =	$874.66		$954.7859	$954.78	$954.75	$954.80