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	$125.78	5.561%	$132.7746	$132.77	$132.75	$132.80
Purchase #2	$60.67	9.626%	$66.5101	$66.51	$66.50	$66.50
Purchase #3	$11.94	11.785%	$13.3471	$13.35	$13.35	$13.30
Purchase #4	$146.99	10.313%	$162.1491	$162.15	$162.15	$162.10
Purchase #5	$10.67	11.123%	$11.8568	$11.86	$11.85	$11.90
Purchase #6	$223.82	4.356%	$233.5696	$233.57	$233.55	$233.60
Purchase #7	$140.38	7.743%	$151.2496	$151.25	$151.25	$151.20
7 purchase totals =	$720.25		$771.4569	$771.46	$771.40	$771.40