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	$160.42	7.723%	$172.8092	$172.81	$172.80	$172.80
Purchase #2	$33.30	11.252%	$37.0469	$37.05	$37.05	$37.00
Purchase #3	$59.86	4.405%	$62.4968	$62.50	$62.50	$62.50
Purchase #4	$83.27	3.458%	$86.1495	$86.15	$86.15	$86.10
Purchase #5	$119.89	13.480%	$136.0512	$136.05	$136.05	$136.10
Purchase #6	$207.71	11.151%	$230.8717	$230.87	$230.85	$230.90
Purchase #7	$59.83	8.672%	$65.0185	$65.02	$65.00	$65.00
7 purchase totals =	$724.28		$790.4438	$790.45	$790.40	$790.40