No, the online version cannot prepare multiple returns in the same account. Only one Federal return can be prepared per online account per year. Each return needs a separate account, separate User ID, and separate fee (if applicable). If you try to prepare a second return in the same account, it will overwrite the first one.
The desktop versions (CD/download), however, can prepare multiple returns with 5 free Federal efiles. Some of the desktop products also include a state program for preparing state returns. There is a 24.99 state efile fee (except free for New York state.) There is no fee to print and mail the state returns.