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	$158.29	5.181%	$166.491	$166.49	$166.50	$166.50
Purchase #2	$196.81	13.385%	$223.153	$223.15	$223.15	$223.20
Purchase #3	$146.45	10.723%	$162.1538	$162.15	$162.15	$162.20
Purchase #4	$93.97	13.606%	$106.7556	$106.76	$106.75	$106.80
Purchase #5	$185.53	5.828%	$196.3427	$196.34	$196.35	$196.30
Purchase #6	$164.85	11.376%	$183.6033	$183.60	$183.60	$183.60
Purchase #7	$87.89	12.678%	$99.0327	$99.03	$99.05	$99.00
7 purchase totals =	$1,033.79		$1,137.5321	$1,137.52	$1,137.55	$1,137.60