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	$223.82	13.147%	$253.2456	$253.25	$253.25	$253.20
Purchase #2	$208.39	13.837%	$237.2249	$237.22	$237.20	$237.20
Purchase #3	$123.72	11.284%	$137.6806	$137.68	$137.70	$137.70
Purchase #4	$83.84	9.178%	$91.5348	$91.53	$91.55	$91.50
Purchase #5	$220.59	3.179%	$227.6026	$227.60	$227.60	$227.60
Purchase #6	$10.72	12.134%	$12.0208	$12.02	$12.00	$12.00
Purchase #7	$171.93	11.470%	$191.6504	$191.65	$191.65	$191.70
7 purchase totals =	$1,043.01		$1,150.9597	$1,150.95	$1,150.95	$1,150.90