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	$98.56	4.814%	$103.3047	$103.30	$103.30	$103.30
Purchase #2	$137.30	3.733%	$142.4254	$142.43	$142.45	$142.40
Purchase #3	$40.81	11.631%	$45.5566	$45.56	$45.55	$45.60
Purchase #4	$136.58	7.213%	$146.4315	$146.43	$146.45	$146.40
Purchase #5	$151.26	7.216%	$162.1749	$162.17	$162.15	$162.20
Purchase #6	$127.76	5.725%	$135.0743	$135.07	$135.05	$135.10
Purchase #7	$107.42	3.813%	$111.5159	$111.52	$111.50	$111.50
7 purchase totals =	$799.69		$846.4833	$846.48	$846.45	$846.50