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	$190.77	7.707%	$205.4726	$205.47	$205.45	$205.50
Purchase #2	$97.38	6.387%	$103.5997	$103.60	$103.60	$103.60
Purchase #3	$211.39	10.521%	$233.6303	$233.63	$233.65	$233.60
Purchase #4	$72.31	11.261%	$80.4528	$80.45	$80.45	$80.50
Purchase #5	$123.27	13.469%	$139.8732	$139.87	$139.85	$139.90
Purchase #6	$209.29	7.538%	$225.0663	$225.07	$225.05	$225.10
Purchase #7	$239.36	10.786%	$265.1774	$265.18	$265.20	$265.20
7 purchase totals =	$1,143.77		$1,253.2723	$1,253.27	$1,253.25	$1,253.40