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	$68.37	3.849%	$71.0016	$71.00	$71.00	$71.00
Purchase #2	$14.89	5.559%	$15.7177	$15.72	$15.70	$15.70
Purchase #3	$130.91	13.177%	$148.16	$148.16	$148.15	$148.20
Purchase #4	$32.57	4.140%	$33.9184	$33.92	$33.90	$33.90
Purchase #5	$133.29	4.679%	$139.5266	$139.53	$139.55	$139.50
Purchase #6	$120.43	10.311%	$132.8475	$132.85	$132.85	$132.80
Purchase #7	$175.25	12.599%	$197.3297	$197.33	$197.35	$197.30
7 purchase totals =	$675.71		$738.5015	$738.51	$738.50	$738.40