There doesn't seem to be a nanosleep function in slitaz, but there is the sleep command for seconds, minutes, hours or days and a usleep function that works in milliseconds.
You can also get the real gnu sleep command by installing the coreutils-command package.
The question is why do you need a command that works in nanoseconds?
I want to send IR code using GPIO pins. So I have to respect the IR protocol thant use bit that are 6.944us long. It is maybe not possible with this interface or Linux. I will probably be block by the scheduler.