If you have the Continue where you left off option selected on the On Startup options menu, you can save all opened windows and tabs by using Chrome's "Exit" feature.
On Windows, select the Chrome menu from an open window, and choose Exit.On Mac, select the Chrome menu from the system menu bar, and choose "Quit Google Chrome."
Note that this is a different way of exiting Chrome than most are used to -- which is to just close the last browser window open. Doing that will only re-open the tabs that were in the last closed window.
