I know there has been debate about this, with some quite severe paces suggested as the crossover. I think it's more about what you feel yourself. For me when doing sub 50 minute pace for 10K I feel I'm 'running' , but often do around 53 pace when training and am conscious that it is more relaxed, but would still consider it a wee bit more than jogging.
I'd say at 26.05 for 5k you're running even if you feel a bit heavy.