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	$83.37	12.260%	$93.5912	$93.59	$93.60	$93.60
Purchase #2	$101.38	10.425%	$111.9489	$111.95	$111.95	$111.90
Purchase #3	$13.68	5.799%	$14.4733	$14.47	$14.45	$14.50
Purchase #4	$10.68	6.621%	$11.3871	$11.39	$11.40	$11.40
Purchase #5	$114.56	7.567%	$123.2288	$123.23	$123.25	$123.20
Purchase #6	$238.35	8.823%	$259.3796	$259.38	$259.40	$259.40
Purchase #7	$173.45	5.465%	$182.929	$182.93	$182.95	$182.90
7 purchase totals =	$735.47		$796.9379	$796.94	$797.00	$796.90