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	$17.31	6.864%	$18.4982	$18.50	$18.50	$18.50
Purchase #2	$13.65	9.363%	$14.928	$14.93	$14.95	$14.90
Purchase #3	$72.86	10.335%	$80.3901	$80.39	$80.40	$80.40
Purchase #4	$117.76	5.178%	$123.8576	$123.86	$123.85	$123.90
Purchase #5	$63.61	13.585%	$72.2514	$72.25	$72.25	$72.30
Purchase #6	$140.95	3.189%	$145.4449	$145.44	$145.45	$145.40
Purchase #7	$10.27	13.262%	$11.632	$11.63	$11.65	$11.60
7 purchase totals =	$436.41		$467.0022	$467.00	$467.05	$467.00