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	$118.59	4.196%	$123.566	$123.57	$123.55	$123.60
Purchase #2	$119.72	12.485%	$134.667	$134.67	$134.65	$134.70
Purchase #3	$127.66	8.107%	$138.0094	$138.01	$138.00	$138.00
Purchase #4	$238.96	10.510%	$264.0747	$264.07	$264.05	$264.10
Purchase #5	$60.29	9.618%	$66.0887	$66.09	$66.10	$66.10
Purchase #6	$155.61	7.471%	$167.2356	$167.24	$167.25	$167.20
Purchase #7	$81.26	11.762%	$90.8178	$90.82	$90.80	$90.80
7 purchase totals =	$902.09		$984.4592	$984.47	$984.40	$984.50