Effect of source output impedance on reflections in a transmission line
You can terminate at either end. 

But load termination prevents reflections. 

Source termination does terminate reflections, if the load is mismatched.

Load termination causes a continual DC draw of current.

Source termination, with the load open circuited, imposes a 50% initial drop in the voltage on the transmission line; thus a 5 volt output (before the Source termination) appears as only 2.5 volts on the line, UNTIL. Until the transition reached end of the (non-loaded) line, where mother nature uses the energy flows and wave-disruptions to sustain the same current while inverting and generating a reverse (reflected) transition, which causes a doubling of the line voltage that sends a 5 volt wave back toward the source. For a single-user at-end-of-line, this is fine. For a multi-use line with users scatters all along the line, some initially see the 0v, then the 2.5v, then finally the 5volt.