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	$131.68	11.487%	$146.8061	$146.81	$146.80	$146.80
Purchase #2	$135.69	12.305%	$152.3867	$152.39	$152.40	$152.40
Purchase #3	$102.92	11.335%	$114.586	$114.59	$114.60	$114.60
Purchase #4	$42.88	8.233%	$46.4103	$46.41	$46.40	$46.40
Purchase #5	$21.28	3.561%	$22.0378	$22.04	$22.05	$22.00
Purchase #6	$45.39	13.836%	$51.6702	$51.67	$51.65	$51.70
Purchase #7	$89.44	12.455%	$100.5798	$100.58	$100.60	$100.60
7 purchase totals =	$569.28		$634.4769	$634.49	$634.50	$634.50