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	$117.30	13.338%	$132.9455	$132.95	$132.95	$132.90
Purchase #2	$93.81	10.871%	$104.0081	$104.01	$104.00	$104.00
Purchase #3	$56.48	11.232%	$62.8238	$62.82	$62.80	$62.80
Purchase #4	$68.28	4.526%	$71.3704	$71.37	$71.35	$71.40
Purchase #5	$12.93	13.395%	$14.662	$14.66	$14.65	$14.70
Purchase #6	$18.39	12.495%	$20.6878	$20.69	$20.70	$20.70
Purchase #7	$152.53	12.782%	$172.0264	$172.03	$172.05	$172.00
7 purchase totals =	$519.72		$578.5240	$578.53	$578.50	$578.50