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	$13.53	6.873%	$14.4599	$14.46	$14.45	$14.50
Purchase #2	$242.34	6.576%	$258.2763	$258.28	$258.30	$258.30
Purchase #3	$89.61	12.852%	$101.1267	$101.13	$101.15	$101.10
Purchase #4	$47.52	4.671%	$49.7397	$49.74	$49.75	$49.70
Purchase #5	$199.32	13.211%	$225.6522	$225.65	$225.65	$225.70
Purchase #6	$32.58	9.307%	$35.6122	$35.61	$35.60	$35.60
Purchase #7	$37.51	13.125%	$42.4332	$42.43	$42.45	$42.40
7 purchase totals =	$662.41		$727.3002	$727.30	$727.35	$727.30