criminal record 321 Criminal Records, Expungement

i live in canada i just recently got a managment job with a retail store they have done a back ground check it was fine i got the job ok fine here the question since getting the job i was with someone in another retail store an they stole something i was charged cause i was with them i was found guiltyof theft under 5000 even though they have done the check will they do it again an can i do anything like get the record sealed or expunged any advice would help