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	$197.30	11.522%	$220.0329	$220.03	$220.05	$220.00
Purchase #2	$179.61	8.437%	$194.7637	$194.76	$194.75	$194.80
Purchase #3	$133.92	3.111%	$138.0863	$138.09	$138.10	$138.10
Purchase #4	$117.83	11.406%	$131.2697	$131.27	$131.25	$131.30
Purchase #5	$146.39	6.540%	$155.9639	$155.96	$155.95	$156.00
Purchase #6	$82.83	9.395%	$90.6119	$90.61	$90.60	$90.60
Purchase #7	$34.47	11.806%	$38.5395	$38.54	$38.55	$38.50
7 purchase totals =	$892.35		$969.2679	$969.26	$969.25	$969.30