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	$106.28	4.790%	$111.3708	$111.37	$111.35	$111.40
Purchase #2	$205.48	9.603%	$225.2122	$225.21	$225.20	$225.20
Purchase #3	$90.29	11.189%	$100.3925	$100.39	$100.40	$100.40
Purchase #4	$231.97	8.355%	$251.3511	$251.35	$251.35	$251.40
Purchase #5	$56.38	11.822%	$63.0452	$63.05	$63.05	$63.00
Purchase #6	$95.54	8.717%	$103.8682	$103.87	$103.85	$103.90
Purchase #7	$98.48	10.453%	$108.7741	$108.77	$108.75	$108.80
7 purchase totals =	$884.42		$964.0141	$964.01	$963.95	$964.10