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	$154.82	4.328%	$161.5206	$161.52	$161.50	$161.50
Purchase #2	$90.44	11.117%	$100.4942	$100.49	$100.50	$100.50
Purchase #3	$133.80	4.110%	$139.2992	$139.30	$139.30	$139.30
Purchase #4	$45.83	4.303%	$47.8021	$47.80	$47.80	$47.80
Purchase #5	$151.39	4.580%	$158.3237	$158.32	$158.30	$158.30
Purchase #6	$94.43	3.726%	$97.9485	$97.95	$97.95	$97.90
Purchase #7	$46.66	9.600%	$51.1394	$51.14	$51.15	$51.10
7 purchase totals =	$717.37		$756.5277	$756.52	$756.50	$756.40