Our SOP is to leave it on Auto at all times except if told directly by ATC to switch it off (which would be standby, no off setting on the box). Hower, normally on taxy in we change the squawk to 2000, from start of december on to 0000.
On SMGCS equipped airports we should leave the assigned squawk in from the time we receive it until we pulled into the gate, however to be honest most forget to leave the squawk in during taxy in except if we get told to re-squawk the old code, LSZH ground controllers for example are very fast to do that.