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	$182.58	12.768%	$205.8918	$205.89	$205.90	$205.90
Purchase #2	$226.92	12.835%	$256.0452	$256.05	$256.05	$256.00
Purchase #3	$180.37	11.343%	$200.8294	$200.83	$200.85	$200.80
Purchase #4	$60.66	6.278%	$64.4682	$64.47	$64.45	$64.50
Purchase #5	$241.55	6.329%	$256.8377	$256.84	$256.85	$256.80
Purchase #6	$98.85	3.758%	$102.5648	$102.56	$102.55	$102.60
Purchase #7	$113.30	11.722%	$126.581	$126.58	$126.60	$126.60
7 purchase totals =	$1,104.23		$1,213.2181	$1,213.22	$1,213.25	$1,213.20