Tipping is 100% optional and investors are still guaranteed to trade via Public with zero-commissions. Tipping is separate from orders and will not affect an investor's order execution.
After an investor submits his order, they will be given an opportunity to tip Public. If the investor decides to tip, they will have to tap the "+" sign until they reach the tip amount they want to give, up to a maximum of 5%. The tip is deducted against the buying power of the account.