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	$241.66	12.821%	$272.6432	$272.64	$272.65	$272.60
Purchase #2	$61.31	13.339%	$69.4881	$69.49	$69.50	$69.50
Purchase #3	$173.66	9.284%	$189.7826	$189.78	$189.80	$189.80
Purchase #4	$155.47	11.867%	$173.9196	$173.92	$173.90	$173.90
Purchase #5	$60.76	6.164%	$64.5052	$64.51	$64.50	$64.50
Purchase #6	$210.59	8.463%	$228.4122	$228.41	$228.40	$228.40
Purchase #7	$15.82	12.680%	$17.826	$17.83	$17.85	$17.80
7 purchase totals =	$919.27		$1,016.5769	$1,016.58	$1,016.60	$1,016.50