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	$50.78	9.467%	$55.5873	$55.59	$55.60	$55.60
Purchase #2	$64.59	5.176%	$67.9332	$67.93	$67.95	$67.90
Purchase #3	$200.25	11.168%	$222.6139	$222.61	$222.60	$222.60
Purchase #4	$82.89	13.643%	$94.1987	$94.20	$94.20	$94.20
Purchase #5	$160.60	11.386%	$178.8859	$178.89	$178.90	$178.90
Purchase #6	$201.52	12.766%	$227.246	$227.25	$227.25	$227.20
Purchase #7	$180.95	8.579%	$196.4737	$196.47	$196.45	$196.50
7 purchase totals =	$941.58		$1,042.9387	$1,042.94	$1,042.95	$1,042.90