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	$225.47	13.667%	$256.285	$256.29	$256.30	$256.30
Purchase #2	$35.86	5.852%	$37.9585	$37.96	$37.95	$38.00
Purchase #3	$9.89	3.726%	$10.2585	$10.26	$10.25	$10.30
Purchase #4	$76.61	9.241%	$83.6895	$83.69	$83.70	$83.70
Purchase #5	$149.83	7.699%	$161.3654	$161.37	$161.35	$161.40
Purchase #6	$126.75	4.685%	$132.6882	$132.69	$132.70	$132.70
Purchase #7	$43.65	4.292%	$45.5235	$45.52	$45.50	$45.50
7 purchase totals =	$668.06		$727.7686	$727.78	$727.75	$727.90