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	$126.29	13.687%	$143.5753	$143.58	$143.60	$143.60
Purchase #2	$131.93	4.252%	$137.5397	$137.54	$137.55	$137.50
Purchase #3	$60.38	3.581%	$62.5422	$62.54	$62.55	$62.50
Purchase #4	$89.90	6.129%	$95.41	$95.41	$95.40	$95.40
Purchase #5	$66.82	11.470%	$74.4843	$74.48	$74.50	$74.50
Purchase #6	$197.76	12.496%	$222.4721	$222.47	$222.45	$222.50
Purchase #7	$17.85	11.325%	$19.8715	$19.87	$19.85	$19.90
7 purchase totals =	$690.93		$755.8951	$755.89	$755.90	$755.90