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	$158.27	7.258%	$169.7572	$169.76	$169.75	$169.80
Purchase #2	$172.67	10.457%	$190.7261	$190.73	$190.75	$190.70
Purchase #3	$143.34	11.218%	$159.4199	$159.42	$159.40	$159.40
Purchase #4	$216.66	10.613%	$239.6541	$239.65	$239.65	$239.70
Purchase #5	$44.58	8.505%	$48.3715	$48.37	$48.35	$48.40
Purchase #6	$90.86	10.631%	$100.5193	$100.52	$100.50	$100.50
Purchase #7	$39.81	6.715%	$42.4832	$42.48	$42.50	$42.50
7 purchase totals =	$866.19		$950.9313	$950.93	$950.90	$951.00