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	$247.71	3.485%	$256.3427	$256.34	$256.35	$256.30
Purchase #2	$26.25	8.486%	$28.4776	$28.48	$28.50	$28.50
Purchase #3	$95.91	4.714%	$100.4312	$100.43	$100.45	$100.40
Purchase #4	$129.79	12.840%	$146.455	$146.46	$146.45	$146.50
Purchase #5	$94.84	5.778%	$100.3199	$100.32	$100.30	$100.30
Purchase #6	$72.72	8.468%	$78.8779	$78.88	$78.90	$78.90
Purchase #7	$7.70	3.735%	$7.9876	$7.99	$8.00	$8.00
7 purchase totals =	$674.92		$718.8919	$718.90	$718.95	$718.90