What's the scam here? If I win I get double coins else I get 5% of what I bet
E[X] = 2.5% On average I get 102.5% of what I bet
When exactly does the casino gets money?

Still in startup phase so yea giving away some doges .. return rate will drop from 5% to 2% in the future ..
This is a lie, you can roll 0 so your casino is still making money even if you return 5% on losing bets on odd/even. For the correct number bet just paying 5x is the biggest rip-off I have ever seen in a casino, even returning 40% of losing bets, this has an EV of -40%. Seems extremely shady to try to make it appear that your casino is giving away Doges.
This casino is 100% made to take your money so you should stay away!
Much sad!