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	$191.87	11.845%	$214.597	$214.60	$214.60	$214.60
Purchase #2	$112.42	5.767%	$118.9033	$118.90	$118.90	$118.90
Purchase #3	$182.52	13.252%	$206.7076	$206.71	$206.70	$206.70
Purchase #4	$33.61	13.522%	$38.1547	$38.15	$38.15	$38.20
Purchase #5	$155.89	8.310%	$168.8445	$168.84	$168.85	$168.80
Purchase #6	$237.78	11.465%	$265.0415	$265.04	$265.05	$265.00
Purchase #7	$47.78	10.601%	$52.8452	$52.85	$52.85	$52.80
7 purchase totals =	$961.87		$1,065.0938	$1,065.09	$1,065.10	$1,065.00