Thanks edgar.  I thought someone might have done this.
 


(defun round (x)
 (cond ((> x 0) (truncate (+ x 0.5)))
       ((= (- x 0.5) (truncate (- x 0.5))) (truncate x))
       (t (truncate (- x 0.5)))))

But I'm glad I didn't have to work this function out myself :-)
George