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	$59.38	9.776%	$65.185	$65.19	$65.20	$65.20
Purchase #2	$94.81	11.379%	$105.5984	$105.60	$105.60	$105.60
Purchase #3	$146.60	8.103%	$158.479	$158.48	$158.50	$158.50
Purchase #4	$157.30	10.167%	$173.2927	$173.29	$173.30	$173.30
Purchase #5	$145.67	4.672%	$152.4757	$152.48	$152.50	$152.50
Purchase #6	$92.28	9.155%	$100.7282	$100.73	$100.75	$100.70
Purchase #7	$136.85	13.180%	$154.8868	$154.89	$154.90	$154.90
7 purchase totals =	$832.89		$910.6458	$910.66	$910.75	$910.70