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	$119.31	13.575%	$135.5063	$135.51	$135.50	$135.50
Purchase #2	$176.90	7.747%	$190.6044	$190.60	$190.60	$190.60
Purchase #3	$42.34	10.801%	$46.9131	$46.91	$46.90	$46.90
Purchase #4	$47.93	7.622%	$51.5832	$51.58	$51.60	$51.60
Purchase #5	$112.70	3.475%	$116.6163	$116.62	$116.60	$116.60
Purchase #6	$101.91	9.348%	$111.4365	$111.44	$111.45	$111.40
Purchase #7	$43.90	3.463%	$45.4203	$45.42	$45.40	$45.40
7 purchase totals =	$644.99		$698.0801	$698.08	$698.05	$698.00