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	$177.51	4.526%	$185.5441	$185.54	$185.55	$185.50
Purchase #2	$5.71	9.710%	$6.2644	$6.26	$6.25	$6.30
Purchase #3	$127.65	7.466%	$137.1803	$137.18	$137.20	$137.20
Purchase #4	$51.96	8.496%	$56.3745	$56.37	$56.35	$56.40
Purchase #5	$56.39	11.613%	$62.9386	$62.94	$62.95	$62.90
Purchase #6	$50.83	10.738%	$56.2881	$56.29	$56.30	$56.30
Purchase #7	$17.84	11.256%	$19.8481	$19.85	$19.85	$19.80
7 purchase totals =	$487.89		$524.4381	$524.43	$524.45	$524.40