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	$42.73	5.414%	$45.0434	$45.04	$45.05	$45.00
Purchase #2	$43.66	5.161%	$45.9133	$45.91	$45.90	$45.90
Purchase #3	$18.42	5.690%	$19.4681	$19.47	$19.45	$19.50
Purchase #4	$200.68	10.220%	$221.1895	$221.19	$221.20	$221.20
Purchase #5	$155.38	6.523%	$165.5154	$165.52	$165.50	$165.50
Purchase #6	$173.86	12.277%	$195.2048	$195.20	$195.20	$195.20
Purchase #7	$194.29	11.433%	$216.5032	$216.50	$216.50	$216.50
7 purchase totals =	$829.02		$908.8377	$908.83	$908.80	$908.80