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	$181.53	5.510%	$191.5323	$191.53	$191.55	$191.50
Purchase #2	$248.38	3.343%	$256.6833	$256.68	$256.70	$256.70
Purchase #3	$102.34	13.781%	$116.4435	$116.44	$116.45	$116.40
Purchase #4	$11.34	4.760%	$11.8798	$11.88	$11.90	$11.90
Purchase #5	$114.85	13.701%	$130.5856	$130.59	$130.60	$130.60
Purchase #6	$131.63	11.109%	$146.2528	$146.25	$146.25	$146.30
Purchase #7	$76.39	11.359%	$85.0671	$85.07	$85.05	$85.10
7 purchase totals =	$866.46		$938.4444	$938.44	$938.50	$938.50