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	$190.85	13.438%	$216.4964	$216.50	$216.50	$216.50
Purchase #2	$75.53	12.754%	$85.1631	$85.16	$85.15	$85.20
Purchase #3	$146.52	12.472%	$164.794	$164.79	$164.80	$164.80
Purchase #4	$102.44	13.567%	$116.338	$116.34	$116.35	$116.30
Purchase #5	$93.65	13.514%	$106.3059	$106.31	$106.30	$106.30
Purchase #6	$62.98	7.697%	$67.8276	$67.83	$67.85	$67.80
Purchase #7	$42.71	13.736%	$48.5766	$48.58	$48.60	$48.60
7 purchase totals =	$714.68		$805.5016	$805.51	$805.55	$805.50