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	$93.72	13.578%	$106.4453	$106.45	$106.45	$106.40
Purchase #2	$32.82	3.425%	$33.9441	$33.94	$33.95	$33.90
Purchase #3	$197.67	8.537%	$214.5451	$214.55	$214.55	$214.50
Purchase #4	$159.85	5.330%	$168.37	$168.37	$168.35	$168.40
Purchase #5	$163.29	6.395%	$173.7324	$173.73	$173.75	$173.70
Purchase #6	$87.78	3.225%	$90.6109	$90.61	$90.60	$90.60
Purchase #7	$151.68	4.549%	$158.5799	$158.58	$158.60	$158.60
7 purchase totals =	$886.81		$946.2277	$946.23	$946.25	$946.10