There is no way to exit without saving in TurboTax Online. Everything you enter is saved immediately and permanently. TurboTax Online is not really suitable for trying out different scenarios. You could use a different user ID than the one you use for your actual tax return, but you would have to do a complete new return from scratch, and you would have to be careful to keep track of your different user IDs and passwords. Also, with TurboTax Online you cannot see the actual tax return unless you pay for the account. You can see the Form 1040, but not the other forms, schedules, or worksheets. With TurboTax Free Edition, you could see a PDF of the entire return without paying, but Free Edition only handles very simple returns, and only Form 1040EZ or 1040A, not 1040.
The CD or download TurboTax software is much better suited to trying out multiple scenarios. You can create as many trial returns as you want, and save each one with a different file name. You can make a copy of a return with a different name and make changes to it, so you don't have to start every test case from scratch. None of this affects your real tax return at all. The CD/download software also has a What-If Worksheet that lets you easily try out different scenarios using a complete return as a starting point, and compare the scenarios side-by-side, without affecting the actual return at all. The CD/download software also allows you to exit without saving if you want to do that.
