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	$246.70	3.829%	$256.1461	$256.15	$256.15	$256.10
Purchase #2	$23.40	3.491%	$24.2169	$24.22	$24.20	$24.20
Purchase #3	$111.71	12.187%	$125.3241	$125.32	$125.30	$125.30
Purchase #4	$46.30	4.385%	$48.3303	$48.33	$48.35	$48.30
Purchase #5	$76.66	6.113%	$81.3462	$81.35	$81.35	$81.30
Purchase #6	$40.40	13.443%	$45.831	$45.83	$45.85	$45.80
Purchase #7	$131.54	11.371%	$146.4974	$146.50	$146.50	$146.50
7 purchase totals =	$676.71		$727.6920	$727.70	$727.70	$727.50