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	$109.89	7.426%	$118.0504	$118.05	$118.05	$118.10
Purchase #2	$50.83	7.133%	$54.4557	$54.46	$54.45	$54.50
Purchase #3	$230.55	3.729%	$239.1472	$239.15	$239.15	$239.10
Purchase #4	$135.52	12.840%	$152.9208	$152.92	$152.90	$152.90
Purchase #5	$158.52	13.632%	$180.1294	$180.13	$180.15	$180.10
Purchase #6	$38.60	7.338%	$41.4325	$41.43	$41.45	$41.40
Purchase #7	$230.97	4.736%	$241.9087	$241.91	$241.90	$241.90
7 purchase totals =	$954.88		$1,028.0447	$1,028.05	$1,028.05	$1,028.00