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	$162.31	7.172%	$173.9509	$173.95	$173.95	$174.00
Purchase #2	$102.40	9.235%	$111.8566	$111.86	$111.85	$111.90
Purchase #3	$140.83	5.410%	$148.4489	$148.45	$148.45	$148.40
Purchase #4	$40.73	12.529%	$45.8331	$45.83	$45.85	$45.80
Purchase #5	$22.25	5.257%	$23.4197	$23.42	$23.40	$23.40
Purchase #6	$151.72	4.522%	$158.5808	$158.58	$158.60	$158.60
Purchase #7	$142.78	8.148%	$154.4137	$154.41	$154.40	$154.40
7 purchase totals =	$763.02		$816.5037	$816.50	$816.50	$816.50