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	$40.60	12.422%	$45.6433	$45.64	$45.65	$45.60
Purchase #2	$56.30	6.490%	$59.9539	$59.95	$59.95	$60.00
Purchase #3	$248.61	10.579%	$274.9105	$274.91	$274.90	$274.90
Purchase #4	$91.58	9.243%	$100.0447	$100.04	$100.05	$100.00
Purchase #5	$243.51	11.177%	$270.7271	$270.73	$270.75	$270.70
Purchase #6	$210.56	9.139%	$229.8031	$229.80	$229.80	$229.80
Purchase #7	$165.64	13.381%	$187.8043	$187.80	$187.80	$187.80
7 purchase totals =	$1,056.80		$1,168.8869	$1,168.87	$1,168.90	$1,168.80