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	$87.48	13.363%	$99.17	$99.17	$99.15	$99.20
Purchase #2	$132.33	11.872%	$148.0402	$148.04	$148.05	$148.00
Purchase #3	$182.27	5.283%	$191.8993	$191.90	$191.90	$191.90
Purchase #4	$190.59	11.461%	$212.4335	$212.43	$212.45	$212.40
Purchase #5	$111.63	8.272%	$120.864	$120.86	$120.85	$120.90
Purchase #6	$227.65	12.431%	$255.9492	$255.95	$255.95	$255.90
Purchase #7	$6.71	13.327%	$7.6042	$7.60	$7.60	$7.60
7 purchase totals =	$938.66		$1,035.9604	$1,035.95	$1,035.95	$1,035.90