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	$74.69	8.619%	$81.1275	$81.13	$81.15	$81.10
Purchase #2	$159.94	11.114%	$177.7157	$177.72	$177.70	$177.70
Purchase #3	$58.93	4.221%	$61.4174	$61.42	$61.40	$61.40
Purchase #4	$231.65	5.246%	$243.8024	$243.80	$243.80	$243.80
Purchase #5	$144.61	4.545%	$151.1825	$151.18	$151.20	$151.20
Purchase #6	$244.68	8.104%	$264.5089	$264.51	$264.50	$264.50
Purchase #7	$33.48	10.544%	$37.0101	$37.01	$37.00	$37.00
7 purchase totals =	$947.98		$1,016.7645	$1,016.77	$1,016.75	$1,016.70