Try the following:

<!-- language: lang-lisp -->

    (defun nxml-jump-to-closing-tag ()
      (interactive)
      (forward-char 2)
      (if (search-backward "<" nil t)
          (nxml-forward-element)
        (message "No more elements")
        )
      )

    (defun nxml-jump-to-openning-tag ()
      (interactive)
      (backward-char 2)
      (if (search-forward ">" nil t)
          (nxml-backward-element)
        (message "No more elements")
        )
      )

    (define-key nxml-mode-map (kbd "<C-M-right>") 'nxml-jump-to-closing-tag)
    (define-key nxml-mode-map (kbd "<C-M-left>") 'nxml-jump-to-openning-tag)

Press `C-M-←`. Press `C-M-→` to get back.