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	$82.31	4.580%	$86.0798	$86.08	$86.10	$86.10
Purchase #2	$37.90	10.486%	$41.8742	$41.87	$41.85	$41.90
Purchase #3	$120.54	10.176%	$132.8062	$132.81	$132.80	$132.80
Purchase #4	$234.93	7.748%	$253.1324	$253.13	$253.15	$253.10
Purchase #5	$104.38	6.385%	$111.0447	$111.04	$111.05	$111.00
Purchase #6	$28.40	10.515%	$31.3863	$31.39	$31.40	$31.40
Purchase #7	$75.60	7.244%	$81.0765	$81.08	$81.10	$81.10
7 purchase totals =	$684.06		$737.4001	$737.40	$737.45	$737.40