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	$201.38	10.539%	$222.6034	$222.60	$222.60	$222.60
Purchase #2	$222.85	10.434%	$246.1022	$246.10	$246.10	$246.10
Purchase #3	$231.45	13.514%	$262.7282	$262.73	$262.75	$262.70
Purchase #4	$117.94	4.668%	$123.4454	$123.45	$123.45	$123.40
Purchase #5	$234.30	13.435%	$265.7782	$265.78	$265.80	$265.80
Purchase #6	$22.26	4.404%	$23.2403	$23.24	$23.25	$23.20
Purchase #7	$131.28	10.222%	$144.6994	$144.70	$144.70	$144.70
7 purchase totals =	$1,161.46		$1,288.5971	$1,288.60	$1,288.65	$1,288.50