You're welcome Lynx.
Typing sensitive information, like that found in a tax return, into a computer you don't have control over is generally an unwise idea.
Keyloggers and trojans are pretty readily available to people who want to cause mischief and the IT staffing to prevent such problems at most internet cafes and public libraries is scant to non-existent.
In the last two months, I've found two key loggers at two local public internet terminals, one was at a local public library, the other was at an internet cafe. In neither case did the staff even realize what a keylogger was or what it could do.
In 2005, I was also involved with investigating a keylogger program that was found on a school system's computer labs network. One of the school system's temporary IT staffers had written and installed it. While he was not prosecuted for doing so—because they couldn't find evidence of anything beyond installing the software, he was fired.
Unfortunately, keylogger hardware is cheap and readily available, as seen
here. And it often looks fairly innoccuous, unless you know what you're looking at.
Of course, physical security of the machines is the first line of defense against things like this, and in a public library or internet cafe, it basically doesn't exist.