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	$32.25	7.725%	$34.7413	$34.74	$34.75	$34.70
Purchase #2	$69.34	11.762%	$77.4958	$77.50	$77.50	$77.50
Purchase #3	$210.61	7.108%	$225.5802	$225.58	$225.60	$225.60
Purchase #4	$138.51	9.144%	$151.1754	$151.18	$151.20	$151.20
Purchase #5	$83.32	7.643%	$89.6881	$89.69	$89.70	$89.70
Purchase #6	$78.78	4.732%	$82.5079	$82.51	$82.50	$82.50
Purchase #7	$17.61	6.186%	$18.6994	$18.70	$18.70	$18.70
7 purchase totals =	$630.42		$679.8881	$679.90	$679.95	$679.90