I agree with Dann: in Spain we also say ''en el minuto cinco''. And yes, it is not a conjunction but a preposition :)
We should also use ''hacia el minuto cinco'' (hacia=towards, to) if you don't want to be so precise. ''En'' in this case would mean ''in that precise moment'', and ''hacia'' aproximate time. Also apromite time prepositions could be the adverb ''alrededor'' ''Alrededor del minuto cinco''/ the preposition ''sobre'' ''sobre el minuto cinco''=both meaning ''around 5th minute''.
¡Saludos!