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	$205.39	11.284%	$228.5662	$228.57	$228.55	$228.60
Purchase #2	$20.86	3.342%	$21.5571	$21.56	$21.55	$21.60
Purchase #3	$10.61	5.667%	$11.2113	$11.21	$11.20	$11.20
Purchase #4	$164.85	13.758%	$187.5301	$187.53	$187.55	$187.50
Purchase #5	$69.42	4.206%	$72.3398	$72.34	$72.35	$72.30
Purchase #6	$132.72	10.649%	$146.8534	$146.85	$146.85	$146.90
Purchase #7	$42.58	6.433%	$45.3192	$45.32	$45.30	$45.30
7 purchase totals =	$646.43		$713.3771	$713.38	$713.35	$713.40