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	$42.96	12.742%	$48.434	$48.43	$48.45	$48.40
Purchase #2	$46.87	8.644%	$50.9214	$50.92	$50.90	$50.90
Purchase #3	$21.80	12.339%	$24.4899	$24.49	$24.50	$24.50
Purchase #4	$95.49	5.462%	$100.7057	$100.71	$100.70	$100.70
Purchase #5	$183.49	8.400%	$198.9032	$198.90	$198.90	$198.90
Purchase #6	$188.66	12.620%	$212.4689	$212.47	$212.45	$212.50
Purchase #7	$234.25	11.250%	$260.6031	$260.60	$260.60	$260.60
7 purchase totals =	$813.52		$896.5262	$896.52	$896.50	$896.50