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	$46.90	7.389%	$50.3654	$50.37	$50.35	$50.40
Purchase #2	$57.56	8.184%	$62.2707	$62.27	$62.25	$62.30
Purchase #3	$66.79	5.822%	$70.6785	$70.68	$70.70	$70.70
Purchase #4	$59.53	3.342%	$61.5195	$61.52	$61.50	$61.50
Purchase #5	$186.90	11.748%	$208.857	$208.86	$208.85	$208.90
Purchase #6	$146.89	3.277%	$151.7036	$151.70	$151.70	$151.70
Purchase #7	$64.27	4.331%	$67.0535	$67.05	$67.05	$67.10
7 purchase totals =	$628.84		$672.4482	$672.45	$672.40	$672.60