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	$126.28	13.811%	$143.7205	$143.72	$143.70	$143.70
Purchase #2	$132.39	5.598%	$139.8012	$139.80	$139.80	$139.80
Purchase #3	$130.86	10.393%	$144.4603	$144.46	$144.45	$144.50
Purchase #4	$40.73	4.420%	$42.5303	$42.53	$42.55	$42.50
Purchase #5	$13.44	10.337%	$14.8293	$14.83	$14.85	$14.80
Purchase #6	$152.93	9.669%	$167.7168	$167.72	$167.70	$167.70
Purchase #7	$198.83	5.375%	$209.5171	$209.52	$209.50	$209.50
7 purchase totals =	$795.46		$862.5755	$862.58	$862.55	$862.50