Question

What is 36.993 to the nearest thousandth

Answer 1

The next larger thousandth is 36.994 .
The next smaller thousandth is  36.992 .
Neither of those is any nearer to  36.993
than  36.993  already is.

The last '3' at the end of 36.993 is in the thousandths' place.
There is no more piece of another thousandth after it.
So  36.993 is already on a complete thousandth, and
there's no rounding required.