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	$182.84	9.462%	$200.1403	$200.14	$200.15	$200.10
Purchase #2	$138.49	5.760%	$146.467	$146.47	$146.45	$146.50
Purchase #3	$241.45	6.327%	$256.7265	$256.73	$256.75	$256.70
Purchase #4	$30.55	4.473%	$31.9165	$31.92	$31.90	$31.90
Purchase #5	$204.61	5.167%	$215.1822	$215.18	$215.20	$215.20
Purchase #6	$12.73	8.637%	$13.8295	$13.83	$13.85	$13.80
Purchase #7	$52.90	3.372%	$54.6838	$54.68	$54.70	$54.70
7 purchase totals =	$863.57		$918.9458	$918.95	$919.00	$918.90