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	$214.71	6.130%	$227.8717	$227.87	$227.85	$227.90
Purchase #2	$172.87	6.834%	$184.6839	$184.68	$184.70	$184.70
Purchase #3	$133.88	13.836%	$152.4036	$152.40	$152.40	$152.40
Purchase #4	$9.61	4.815%	$10.0727	$10.07	$10.05	$10.10
Purchase #5	$123.33	11.548%	$137.5721	$137.57	$137.55	$137.60
Purchase #6	$138.82	13.511%	$157.576	$157.58	$157.60	$157.60
Purchase #7	$103.31	5.127%	$108.6067	$108.61	$108.60	$108.60
7 purchase totals =	$896.53		$978.7867	$978.78	$978.75	$978.90