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	$44.44	3.514%	$46.0016	$46.00	$46.00	$46.00
Purchase #2	$125.78	12.746%	$141.8119	$141.81	$141.80	$141.80
Purchase #3	$184.64	12.854%	$208.3736	$208.37	$208.35	$208.40
Purchase #4	$62.82	10.660%	$69.5166	$69.52	$69.50	$69.50
Purchase #5	$131.83	5.860%	$139.5552	$139.56	$139.55	$139.60
Purchase #6	$202.66	13.776%	$230.5784	$230.58	$230.60	$230.60
Purchase #7	$104.94	6.236%	$111.4841	$111.48	$111.50	$111.50
7 purchase totals =	$857.11		$947.3214	$947.32	$947.30	$947.40