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	$232.37	7.869%	$250.6552	$250.66	$250.65	$250.70
Purchase #2	$125.87	9.563%	$137.9069	$137.91	$137.90	$137.90
Purchase #3	$247.93	11.263%	$275.8544	$275.85	$275.85	$275.90
Purchase #4	$63.28	6.814%	$67.5919	$67.59	$67.60	$67.60
Purchase #5	$30.76	4.254%	$32.0685	$32.07	$32.05	$32.10
Purchase #6	$20.74	3.417%	$21.4487	$21.45	$21.45	$21.40
Purchase #7	$238.80	11.714%	$266.773	$266.77	$266.75	$266.80
7 purchase totals =	$959.75		$1,052.2986	$1,052.30	$1,052.25	$1,052.40