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	$137.26	11.343%	$152.8294	$152.83	$152.85	$152.80
Purchase #2	$67.70	5.643%	$71.5203	$71.52	$71.50	$71.50
Purchase #3	$62.58	13.662%	$71.1297	$71.13	$71.15	$71.10
Purchase #4	$87.60	5.220%	$92.1727	$92.17	$92.15	$92.20
Purchase #5	$163.51	10.555%	$180.7685	$180.77	$180.75	$180.80
Purchase #6	$17.33	10.603%	$19.1675	$19.17	$19.15	$19.20
Purchase #7	$231.74	6.402%	$246.576	$246.58	$246.60	$246.60
7 purchase totals =	$767.72		$834.1641	$834.17	$834.15	$834.20