As far as most people know, this game is unhackable, which is why it gets requested all the time.
This game's currency values are stored server-side, meaning that even if you are able to temporarily change the value of the currency, if you were to save your game (under the game's settings) or restart the app, the values would change. That means you'd need to get a live data viewer and editor directly on your iDevice and use the hacked currency right away, but even then, the values could be stored separately from what they appear. (i.e. The game could show that you have 25 megabucks but they are stored under a different value, possibly float, such as 11.68) I'm not sure if a data editor has been tested on this game or not, so I can't say whether the answer is clear, but you'd need at minimum a Jailbroken iDevice.