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	$53.71	10.808%	$59.515	$59.52	$59.50	$59.50
Purchase #2	$10.96	3.799%	$11.3764	$11.38	$11.40	$11.40
Purchase #3	$124.54	4.870%	$130.6051	$130.61	$130.60	$130.60
Purchase #4	$139.40	8.601%	$151.3898	$151.39	$151.40	$151.40
Purchase #5	$36.32	11.579%	$40.5255	$40.53	$40.55	$40.50
Purchase #6	$155.49	13.804%	$176.9538	$176.95	$176.95	$177.00
Purchase #7	$44.43	3.700%	$46.0739	$46.07	$46.05	$46.10
7 purchase totals =	$564.85		$616.4395	$616.45	$616.45	$616.50