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	$12.75	12.681%	$14.3668	$14.37	$14.35	$14.40
Purchase #2	$37.46	9.493%	$41.0161	$41.02	$41.00	$41.00
Purchase #3	$112.51	3.209%	$116.1204	$116.12	$116.10	$116.10
Purchase #4	$96.34	4.702%	$100.8699	$100.87	$100.85	$100.90
Purchase #5	$144.99	5.445%	$152.8847	$152.88	$152.90	$152.90
Purchase #6	$183.78	11.830%	$205.5212	$205.52	$205.50	$205.50
Purchase #7	$150.57	13.402%	$170.7494	$170.75	$170.75	$170.70
7 purchase totals =	$738.40		$801.5285	$801.53	$801.45	$801.50