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	$153.87	12.342%	$172.8606	$172.86	$172.85	$172.90
Purchase #2	$135.92	6.348%	$144.5482	$144.55	$144.55	$144.50
Purchase #3	$171.46	13.400%	$194.4356	$194.44	$194.45	$194.40
Purchase #4	$36.90	8.852%	$40.1664	$40.17	$40.15	$40.20
Purchase #5	$144.46	4.579%	$151.0748	$151.07	$151.05	$151.10
Purchase #6	$67.27	11.168%	$74.7827	$74.78	$74.80	$74.80
Purchase #7	$162.71	11.484%	$181.3956	$181.40	$181.40	$181.40
7 purchase totals =	$872.59		$959.2639	$959.27	$959.25	$959.30