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	$43.46	12.416%	$48.856	$48.86	$48.85	$48.90
Purchase #2	$10.51	4.332%	$10.9653	$10.97	$10.95	$11.00
Purchase #3	$12.46	11.746%	$13.9236	$13.92	$13.90	$13.90
Purchase #4	$151.96	11.721%	$169.7712	$169.77	$169.75	$169.80
Purchase #5	$208.55	8.170%	$225.5885	$225.59	$225.60	$225.60
Purchase #6	$36.64	10.556%	$40.5077	$40.51	$40.50	$40.50
Purchase #7	$94.95	4.681%	$99.3946	$99.39	$99.40	$99.40
7 purchase totals =	$558.53		$609.0069	$609.01	$608.95	$609.10