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	$231.51	11.812%	$258.856	$258.86	$258.85	$258.90
Purchase #2	$26.30	3.174%	$27.1348	$27.13	$27.15	$27.10
Purchase #3	$124.82	9.637%	$136.8489	$136.85	$136.85	$136.80
Purchase #4	$32.78	6.588%	$34.9395	$34.94	$34.95	$34.90
Purchase #5	$184.40	4.564%	$192.816	$192.82	$192.80	$192.80
Purchase #6	$238.56	5.136%	$250.8124	$250.81	$250.80	$250.80
Purchase #7	$149.85	12.518%	$168.6082	$168.61	$168.60	$168.60
7 purchase totals =	$988.22		$1,070.0158	$1,070.02	$1,070.00	$1,069.90