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	$118.96	9.684%	$130.4801	$130.48	$130.50	$130.50
Purchase #2	$207.26	3.531%	$214.5784	$214.58	$214.60	$214.60
Purchase #3	$64.30	5.156%	$67.6153	$67.62	$67.60	$67.60
Purchase #4	$20.35	5.505%	$21.4703	$21.47	$21.45	$21.50
Purchase #5	$151.95	5.521%	$160.3392	$160.34	$160.35	$160.30
Purchase #6	$5.71	11.142%	$6.3462	$6.35	$6.35	$6.30
Purchase #7	$163.67	13.186%	$185.2515	$185.25	$185.25	$185.30
7 purchase totals =	$732.20		$786.0810	$786.09	$786.10	$786.10