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	$32.29	13.677%	$36.7063	$36.71	$36.70	$36.70
Purchase #2	$239.41	12.556%	$269.4703	$269.47	$269.45	$269.50
Purchase #3	$243.49	6.741%	$259.9037	$259.90	$259.90	$259.90
Purchase #4	$222.35	9.205%	$242.8173	$242.82	$242.80	$242.80
Purchase #5	$242.37	13.859%	$275.9601	$275.96	$275.95	$276.00
Purchase #6	$132.86	13.816%	$151.2159	$151.22	$151.20	$151.20
Purchase #7	$132.66	10.442%	$146.5124	$146.51	$146.50	$146.50
7 purchase totals =	$1,245.43		$1,382.5860	$1,382.59	$1,382.50	$1,382.60