Not a lawyer, but I'm with Clinton on this one as you can't come to a complete stop after landing if you haven't actually taken off. To me the logical answer (not the legal one) is that you should only log from first moving ... until the decision not to take off is made. Once you've decided to return to the gate/ramp/hanger you are no longer taxiing under your own power for the purpose of take off.
However this makes for an interesting conundrum for us barefoot pilots - does a seaplane ever truly come to rest on the water? Leadsled your thoughts?