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	$165.86	3.798%	$172.1594	$172.16	$172.15	$172.20
Purchase #2	$40.94	13.485%	$46.4608	$46.46	$46.45	$46.50
Purchase #3	$69.73	7.672%	$75.0797	$75.08	$75.10	$75.10
Purchase #4	$50.62	4.719%	$53.0088	$53.01	$53.00	$53.00
Purchase #5	$159.83	7.670%	$172.089	$172.09	$172.10	$172.10
Purchase #6	$24.27	9.160%	$26.4931	$26.49	$26.50	$26.50
Purchase #7	$143.32	13.221%	$162.2683	$162.27	$162.25	$162.30
7 purchase totals =	$654.57		$707.5591	$707.56	$707.55	$707.70