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	$158.80	9.291%	$173.5541	$173.55	$173.55	$173.60
Purchase #2	$32.33	7.363%	$34.7105	$34.71	$34.70	$34.70
Purchase #3	$68.58	5.724%	$72.5055	$72.51	$72.50	$72.50
Purchase #4	$23.87	9.587%	$26.1584	$26.16	$26.15	$26.20
Purchase #5	$82.73	8.667%	$89.9002	$89.90	$89.90	$89.90
Purchase #6	$125.85	11.503%	$140.3265	$140.33	$140.35	$140.30
Purchase #7	$9.49	8.683%	$10.314	$10.31	$10.30	$10.30
7 purchase totals =	$501.65		$547.4692	$547.47	$547.45	$547.50