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	$104.73	6.576%	$111.617	$111.62	$111.60	$111.60
Purchase #2	$83.39	5.187%	$87.7154	$87.72	$87.70	$87.70
Purchase #3	$81.72	8.369%	$88.5591	$88.56	$88.55	$88.60
Purchase #4	$48.54	13.148%	$54.922	$54.92	$54.90	$54.90
Purchase #5	$6.50	10.225%	$7.1646	$7.16	$7.15	$7.20
Purchase #6	$10.79	13.867%	$12.2862	$12.29	$12.30	$12.30
Purchase #7	$202.98	8.444%	$220.1196	$220.12	$220.10	$220.10
7 purchase totals =	$538.65		$582.3839	$582.39	$582.30	$582.40