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	$249.35	5.310%	$262.5905	$262.59	$262.60	$262.60
Purchase #2	$56.90	5.497%	$60.0278	$60.03	$60.05	$60.00
Purchase #3	$184.44	10.369%	$203.5646	$203.56	$203.55	$203.60
Purchase #4	$137.28	6.846%	$146.6782	$146.68	$146.70	$146.70
Purchase #5	$101.50	10.233%	$111.8865	$111.89	$111.90	$111.90
Purchase #6	$131.70	7.185%	$141.1626	$141.16	$141.15	$141.20
Purchase #7	$243.25	11.659%	$271.6105	$271.61	$271.60	$271.60
7 purchase totals =	$1,104.42		$1,197.5207	$1,197.52	$1,197.55	$1,197.60