I actually found a solution. I worked on this for a while and came up with this:
AdjTimeIn: TimeSerial(Int(Int((Hour([TimeIn])+((Minute([TimeIn])+15)/60))*2)/2),((Int((Hour([TimeIn])+((Minute([TimeIn])+15)/60))*2)/2)-Int(Int((Hour([TimeIn])+((Minute([TimeIn])+15)/60))*2)/2))*60,0)
attached is...