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	$102.83	8.383%	$111.4502	$111.45	$111.45	$111.50
Purchase #2	$55.53	9.848%	$60.9986	$61.00	$61.00	$61.00
Purchase #3	$138.99	11.222%	$154.5875	$154.59	$154.60	$154.60
Purchase #4	$38.32	4.721%	$40.1291	$40.13	$40.15	$40.10
Purchase #5	$60.81	10.285%	$67.0643	$67.06	$67.05	$67.10
Purchase #6	$166.47	11.420%	$185.4809	$185.48	$185.50	$185.50
Purchase #7	$180.99	5.793%	$191.4748	$191.47	$191.45	$191.50
7 purchase totals =	$743.94		$811.1854	$811.18	$811.20	$811.30