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	$148.50	8.498%	$161.1195	$161.12	$161.10	$161.10
Purchase #2	$70.72	9.547%	$77.4716	$77.47	$77.45	$77.50
Purchase #3	$69.51	3.362%	$71.8469	$71.85	$71.85	$71.80
Purchase #4	$228.75	12.152%	$256.5477	$256.55	$256.55	$256.50
Purchase #5	$229.27	7.762%	$247.0659	$247.07	$247.05	$247.10
Purchase #6	$37.26	13.468%	$42.2782	$42.28	$42.30	$42.30
Purchase #7	$88.44	5.508%	$93.3113	$93.31	$93.30	$93.30
7 purchase totals =	$872.45		$949.6411	$949.65	$949.60	$949.60