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	$215.77	5.247%	$227.0915	$227.09	$227.10	$227.10
Purchase #2	$235.85	4.238%	$245.8453	$245.85	$245.85	$245.80
Purchase #3	$50.29	7.472%	$54.0477	$54.05	$54.05	$54.00
Purchase #4	$129.54	12.808%	$146.1315	$146.13	$146.15	$146.10
Purchase #5	$47.64	6.226%	$50.6061	$50.61	$50.60	$50.60
Purchase #6	$202.51	13.715%	$230.2842	$230.28	$230.30	$230.30
Purchase #7	$77.88	9.733%	$85.4601	$85.46	$85.45	$85.50
7 purchase totals =	$959.48		$1,039.4664	$1,039.47	$1,039.50	$1,039.40