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	$140.98	5.802%	$149.1597	$149.16	$149.15	$149.20
Purchase #2	$130.63	6.674%	$139.3482	$139.35	$139.35	$139.30
Purchase #3	$184.61	13.434%	$209.4105	$209.41	$209.40	$209.40
Purchase #4	$65.85	6.793%	$70.3232	$70.32	$70.30	$70.30
Purchase #5	$231.48	10.668%	$256.1743	$256.17	$256.15	$256.20
Purchase #6	$129.68	10.243%	$142.9631	$142.96	$142.95	$143.00
Purchase #7	$78.39	9.490%	$85.8292	$85.83	$85.85	$85.80
7 purchase totals =	$961.62		$1,053.2082	$1,053.20	$1,053.15	$1,053.20