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	$106.25	11.226%	$118.1776	$118.18	$118.20	$118.20
Purchase #2	$236.38	7.823%	$254.872	$254.87	$254.85	$254.90
Purchase #3	$132.39	11.359%	$147.4282	$147.43	$147.45	$147.40
Purchase #4	$200.91	11.477%	$223.9684	$223.97	$223.95	$224.00
Purchase #5	$19.67	10.734%	$21.7814	$21.78	$21.80	$21.80
Purchase #6	$119.30	7.106%	$127.7775	$127.78	$127.80	$127.80
Purchase #7	$126.53	10.527%	$139.8498	$139.85	$139.85	$139.80
7 purchase totals =	$941.43		$1,033.8549	$1,033.86	$1,033.90	$1,033.90