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	$37.53	13.135%	$42.4596	$42.46	$42.45	$42.50
Purchase #2	$60.59	11.337%	$67.4591	$67.46	$67.45	$67.50
Purchase #3	$12.59	13.110%	$14.2405	$14.24	$14.25	$14.20
Purchase #4	$28.34	4.103%	$29.5028	$29.50	$29.50	$29.50
Purchase #5	$177.70	9.325%	$194.2705	$194.27	$194.25	$194.30
Purchase #6	$79.68	9.795%	$87.4847	$87.48	$87.50	$87.50
Purchase #7	$18.45	5.822%	$19.5242	$19.52	$19.50	$19.50
7 purchase totals =	$414.88		$454.9414	$454.93	$454.90	$455.00