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	$214.29	12.637%	$241.3698	$241.37	$241.35	$241.40
Purchase #2	$153.61	10.567%	$169.842	$169.84	$169.85	$169.80
Purchase #3	$111.54	9.314%	$121.9288	$121.93	$121.95	$121.90
Purchase #4	$57.52	3.579%	$59.5786	$59.58	$59.60	$59.60
Purchase #5	$90.33	13.112%	$102.1741	$102.17	$102.15	$102.20
Purchase #6	$29.88	13.351%	$33.8693	$33.87	$33.85	$33.90
Purchase #7	$164.55	7.388%	$176.707	$176.71	$176.70	$176.70
7 purchase totals =	$821.72		$905.4696	$905.47	$905.45	$905.50