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	$75.64	3.567%	$78.3381	$78.34	$78.35	$78.30
Purchase #2	$213.89	5.574%	$225.8122	$225.81	$225.80	$225.80
Purchase #3	$228.44	10.265%	$251.8894	$251.89	$251.90	$251.90
Purchase #4	$146.67	12.733%	$165.3455	$165.35	$165.35	$165.30
Purchase #5	$98.71	8.465%	$107.0658	$107.07	$107.05	$107.10
Purchase #6	$67.94	5.396%	$71.606	$71.61	$71.60	$71.60
Purchase #7	$122.26	9.227%	$133.5409	$133.54	$133.55	$133.50
7 purchase totals =	$953.55		$1,033.5979	$1,033.61	$1,033.60	$1,033.50