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	$119.70	10.668%	$132.4696	$132.47	$132.45	$132.50
Purchase #2	$124.91	11.872%	$139.7393	$139.74	$139.75	$139.70
Purchase #3	$86.75	5.152%	$91.2194	$91.22	$91.20	$91.20
Purchase #4	$13.81	12.258%	$15.5028	$15.50	$15.50	$15.50
Purchase #5	$204.91	8.559%	$222.4482	$222.45	$222.45	$222.40
Purchase #6	$70.63	4.244%	$73.6275	$73.63	$73.65	$73.60
Purchase #7	$9.57	13.560%	$10.8677	$10.87	$10.85	$10.90
7 purchase totals =	$630.28		$685.8745	$685.88	$685.85	$685.80