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	$116.70	13.598%	$132.5689	$132.57	$132.55	$132.60
Purchase #2	$99.58	7.833%	$107.3801	$107.38	$107.40	$107.40
Purchase #3	$241.37	11.824%	$269.9096	$269.91	$269.90	$269.90
Purchase #4	$10.38	13.147%	$11.7447	$11.74	$11.75	$11.70
Purchase #5	$133.89	13.748%	$152.2972	$152.30	$152.30	$152.30
Purchase #6	$105.50	5.780%	$111.5979	$111.60	$111.60	$111.60
Purchase #7	$93.97	10.577%	$103.9092	$103.91	$103.90	$103.90
7 purchase totals =	$801.39		$889.4076	$889.41	$889.40	$889.40