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	$54.45	13.389%	$61.7403	$61.74	$61.75	$61.70
Purchase #2	$227.50	13.662%	$258.5811	$258.58	$258.60	$258.60
Purchase #3	$14.87	3.780%	$15.4321	$15.43	$15.45	$15.40
Purchase #4	$24.92	11.189%	$27.7083	$27.71	$27.70	$27.70
Purchase #5	$107.52	5.127%	$113.0326	$113.03	$113.05	$113.00
Purchase #6	$35.96	13.667%	$40.8747	$40.87	$40.85	$40.90
Purchase #7	$128.96	4.270%	$134.4666	$134.47	$134.45	$134.50
7 purchase totals =	$594.18		$651.8357	$651.83	$651.85	$651.80