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	$61.51	7.218%	$65.9498	$65.95	$65.95	$65.90
Purchase #2	$103.45	10.201%	$114.0029	$114.00	$114.00	$114.00
Purchase #3	$100.74	10.272%	$111.088	$111.09	$111.10	$111.10
Purchase #4	$197.43	12.168%	$221.4533	$221.45	$221.45	$221.50
Purchase #5	$81.90	6.534%	$87.2513	$87.25	$87.25	$87.30
Purchase #6	$155.71	6.192%	$165.3516	$165.35	$165.35	$165.40
Purchase #7	$39.78	7.339%	$42.6995	$42.70	$42.70	$42.70
7 purchase totals =	$740.52		$807.7964	$807.79	$807.80	$807.90