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	$58.57	12.595%	$65.9469	$65.95	$65.95	$65.90
Purchase #2	$175.71	11.661%	$196.1995	$196.20	$196.20	$196.20
Purchase #3	$127.78	10.832%	$141.6211	$141.62	$141.60	$141.60
Purchase #4	$117.51	4.187%	$122.4301	$122.43	$122.45	$122.40
Purchase #5	$162.52	6.368%	$172.8693	$172.87	$172.85	$172.90
Purchase #6	$18.55	5.382%	$19.5484	$19.55	$19.55	$19.50
Purchase #7	$242.65	9.513%	$265.7333	$265.73	$265.75	$265.70
7 purchase totals =	$903.29		$984.3486	$984.35	$984.35	$984.20