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	$201.85	7.737%	$217.4671	$217.47	$217.45	$217.50
Purchase #2	$215.75	13.788%	$245.4976	$245.50	$245.50	$245.50
Purchase #3	$52.48	12.848%	$59.2226	$59.22	$59.20	$59.20
Purchase #4	$11.40	12.433%	$12.8174	$12.82	$12.80	$12.80
Purchase #5	$91.58	4.503%	$95.7038	$95.70	$95.70	$95.70
Purchase #6	$67.91	6.426%	$72.2739	$72.27	$72.25	$72.30
Purchase #7	$210.26	8.778%	$228.7166	$228.72	$228.70	$228.70
7 purchase totals =	$851.23		$931.6990	$931.70	$931.60	$931.70