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	$248.77	13.105%	$281.3713	$281.37	$281.35	$281.40
Purchase #2	$236.68	8.367%	$256.483	$256.48	$256.50	$256.50
Purchase #3	$241.41	12.235%	$270.9465	$270.95	$270.95	$270.90
Purchase #4	$135.92	11.491%	$151.5386	$151.54	$151.55	$151.50
Purchase #5	$221.70	11.658%	$247.5458	$247.55	$247.55	$247.50
Purchase #6	$161.70	10.617%	$178.8677	$178.87	$178.85	$178.90
Purchase #7	$200.54	4.139%	$208.8404	$208.84	$208.85	$208.80
7 purchase totals =	$1,446.72		$1,595.5933	$1,595.60	$1,595.60	$1,595.50