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	$35.37	3.760%	$36.6999	$36.70	$36.70	$36.70
Purchase #2	$214.25	10.494%	$236.7334	$236.73	$236.75	$236.70
Purchase #3	$25.82	6.619%	$27.529	$27.53	$27.55	$27.50
Purchase #4	$97.43	8.445%	$105.658	$105.66	$105.65	$105.70
Purchase #5	$99.60	11.761%	$111.314	$111.31	$111.30	$111.30
Purchase #6	$48.78	11.136%	$54.2121	$54.21	$54.20	$54.20
Purchase #7	$164.58	4.713%	$172.3367	$172.34	$172.35	$172.30
7 purchase totals =	$685.83		$744.4831	$744.48	$744.50	$744.40