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	$206.41	10.180%	$227.4225	$227.42	$227.40	$227.40
Purchase #2	$208.60	13.104%	$235.9349	$235.93	$235.95	$235.90
Purchase #3	$90.69	4.203%	$94.5017	$94.50	$94.50	$94.50
Purchase #4	$105.42	12.370%	$118.4605	$118.46	$118.45	$118.50
Purchase #5	$28.26	13.565%	$32.0935	$32.09	$32.10	$32.10
Purchase #6	$225.41	7.733%	$242.841	$242.84	$242.85	$242.80
Purchase #7	$88.95	7.338%	$95.4772	$95.48	$95.50	$95.50
7 purchase totals =	$953.74		$1,046.7313	$1,046.72	$1,046.75	$1,046.70