Any township issuing bonds under this act shall annually levy a tax sufficient to pay the interest thereon, and after five years an amount sufficient to create a sinking fund to pay the principal at maturity; and any township purchasing or acquiring or acting as trustee for grounds for a park or parks, or cemetery or cemeteries is empowered and authorized to annually levy and collect a tax to provide a fund for the purpose of meeting the annual expense of such grounds, and such other improvements as the township board deems necessary.