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	$205.92	10.699%	$227.9514	$227.95	$227.95	$228.00
Purchase #2	$249.65	13.623%	$283.6598	$283.66	$283.65	$283.70
Purchase #3	$117.83	10.624%	$130.3483	$130.35	$130.35	$130.30
Purchase #4	$152.54	8.684%	$165.7866	$165.79	$165.80	$165.80
Purchase #5	$199.42	11.767%	$222.8858	$222.89	$222.90	$222.90
Purchase #6	$71.75	9.715%	$78.7205	$78.72	$78.70	$78.70
Purchase #7	$142.28	11.545%	$158.7062	$158.71	$158.70	$158.70
7 purchase totals =	$1,139.39		$1,268.0586	$1,268.07	$1,268.05	$1,268.10