The total money Jerry needs to make for 5 days to get $50 per night is 5 nights * $50/night = $<<5*50=250>>250.
His total earnings for the past four days is $20 + $60 + $15 + $40 = $<<20+60+15+40=135>>135.
So, Jerry needs to earn $250 - $135 = $<<250-135=115>>115 in tips tonight.
#### 115