[Discuss-gnuradio] Is it possible to make sub-micro seconds level timing control?

Hello,

I have a quick question.

In UHD, is it possible to give a nano second level timing control in timed_tx samples sample?

I think that is possible due to the restriction from OS, 

but I saw some consistent difference in the transmission when I gave timed delay as

1.000000100, 1.000000200, and 1.000000210