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	$34.87	6.565%	$37.1592	$37.16	$37.15	$37.20
Purchase #2	$194.61	8.708%	$211.5566	$211.56	$211.55	$211.60
Purchase #3	$123.45	5.724%	$130.5163	$130.52	$130.50	$130.50
Purchase #4	$107.58	10.578%	$118.9598	$118.96	$118.95	$119.00
Purchase #5	$242.51	13.459%	$275.1494	$275.15	$275.15	$275.10
Purchase #6	$235.70	6.285%	$250.5137	$250.51	$250.50	$250.50
Purchase #7	$13.66	3.495%	$14.1374	$14.14	$14.15	$14.10
7 purchase totals =	$952.38		$1,037.9924	$1,038.00	$1,037.95	$1,038.00