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	$83.42	8.577%	$90.5749	$90.57	$90.55	$90.60
Purchase #2	$27.84	6.534%	$29.6591	$29.66	$29.65	$29.70
Purchase #3	$18.57	13.680%	$21.1104	$21.11	$21.10	$21.10
Purchase #4	$64.58	11.564%	$72.048	$72.05	$72.05	$72.00
Purchase #5	$70.30	3.117%	$72.4913	$72.49	$72.50	$72.50
Purchase #6	$112.60	7.474%	$121.0157	$121.02	$121.00	$121.00
Purchase #7	$49.92	9.105%	$54.4652	$54.47	$54.45	$54.50
7 purchase totals =	$427.23		$461.3646	$461.37	$461.30	$461.40