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	$105.42	11.307%	$117.3398	$117.34	$117.35	$117.30
Purchase #2	$184.85	4.260%	$192.7246	$192.72	$192.70	$192.70
Purchase #3	$190.84	13.189%	$216.0099	$216.01	$216.00	$216.00
Purchase #4	$63.82	3.531%	$66.0735	$66.07	$66.05	$66.10
Purchase #5	$40.31	8.699%	$43.8166	$43.82	$43.80	$43.80
Purchase #6	$160.82	7.780%	$173.3318	$173.33	$173.35	$173.30
Purchase #7	$224.59	9.468%	$245.8542	$245.85	$245.85	$245.90
7 purchase totals =	$970.65		$1,055.1504	$1,055.14	$1,055.10	$1,055.10