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	$187.94	13.259%	$212.859	$212.86	$212.85	$212.90
Purchase #2	$43.70	6.635%	$46.5995	$46.60	$46.60	$46.60
Purchase #3	$234.42	9.299%	$256.2187	$256.22	$256.20	$256.20
Purchase #4	$89.53	7.105%	$95.8911	$95.89	$95.90	$95.90
Purchase #5	$28.35	13.208%	$32.0945	$32.09	$32.10	$32.10
Purchase #6	$79.75	8.300%	$86.3693	$86.37	$86.35	$86.40
Purchase #7	$158.85	10.462%	$175.4689	$175.47	$175.45	$175.50
7 purchase totals =	$822.54		$905.5010	$905.50	$905.45	$905.60