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	$241.74	8.663%	$262.6819	$262.68	$262.70	$262.70
Purchase #2	$41.85	4.129%	$43.578	$43.58	$43.60	$43.60
Purchase #3	$117.58	9.551%	$128.8101	$128.81	$128.80	$128.80
Purchase #4	$158.66	8.793%	$172.611	$172.61	$172.60	$172.60
Purchase #5	$217.80	3.727%	$225.9174	$225.92	$225.90	$225.90
Purchase #6	$42.97	5.621%	$45.3853	$45.39	$45.40	$45.40
Purchase #7	$88.85	11.492%	$99.0606	$99.06	$99.05	$99.10
7 purchase totals =	$909.45		$978.0443	$978.05	$978.05	$978.10