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	$42.63	10.540%	$47.1232	$47.12	$47.10	$47.10
Purchase #2	$135.91	9.130%	$148.3186	$148.32	$148.30	$148.30
Purchase #3	$85.94	10.667%	$95.1072	$95.11	$95.10	$95.10
Purchase #4	$216.53	4.162%	$225.542	$225.54	$225.55	$225.50
Purchase #5	$144.72	9.392%	$158.3121	$158.31	$158.30	$158.30
Purchase #6	$11.39	6.540%	$12.1349	$12.13	$12.15	$12.10
Purchase #7	$192.48	8.345%	$208.5425	$208.54	$208.55	$208.50
7 purchase totals =	$829.60		$895.0805	$895.07	$895.05	$894.90