How do I get the Register to auto fill todays date instead of the last entered date?

Press the "t" key while in the date field for the new transaction. That sets the date back to the current day. It works this way because many people enter receipts sequentially for several days at a time. If that's how you enter transactions then resetting the date back to today for every new transaction would be infuriating and there's no shortcut for selecting "the date of the last transaction entered".