You continue to pray the rosary the same way throughout. If your intention is to pray a Chaplet (a single set of mysteries) at the end of the fifth mystery you will come back to the joiner, this is where the decades all join with the lower part of the rosary which contains the cross.  When you come to the joiner, you decide whether or not you wish to say another Chaplet or end.  If you decide to say another Chaplet you simply announce the next mystery and continue. If you wish to end, you simply say the Glory Be To The Father, the O My Jesus, The Our Father and end the rosary with the Hail Holy Queen and the sign of the Cross.