The "File History" feature allows you to inspect how a single file evolved in detail - by listing only those commits in which the file was changed.
Selecting a File in Your Working Copy
One way to access a single file's commit history is through Tower's Working Copy view.
If the file in question isn't currently modified, remember to have Tower display all of your project's files (not just the modified ones) via the "View" main menu.
Simply right-click the file and choose.
Searching for a File Path
Another way is to search for a file in one of Tower's History views (either directly via the "History" item or by selecting a branch or tag in the sidebar).
Make sure that you select the "File" category in the search textfield on the top right of the window.
Then, enter the file's complete path, from the root folder of the repository. Tower helps you by suggesting & autocompleting path components right as you type.
In both cases, the list of revisions will then only contain commits where this particular file was involved.