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	$53.48	11.849%	$59.8168	$59.82	$59.80	$59.80
Purchase #2	$247.88	8.762%	$269.5992	$269.60	$269.60	$269.60
Purchase #3	$21.72	11.345%	$24.1841	$24.18	$24.20	$24.20
Purchase #4	$44.98	7.564%	$48.3823	$48.38	$48.40	$48.40
Purchase #5	$173.93	12.384%	$195.4695	$195.47	$195.45	$195.50
Purchase #6	$208.62	10.761%	$231.0696	$231.07	$231.05	$231.10
Purchase #7	$144.54	4.621%	$151.2192	$151.22	$151.20	$151.20
7 purchase totals =	$895.15		$979.7407	$979.74	$979.70	$979.80