rounding - How to round float numbers in javascript?

#short
#javascript
#rounding
I need to round for example 6.688689 to 6.7, but it always shows me 7.
My method:
Math.round(6.688689);
//or
Math.round(6.688689, 1);
//or
Math.round(6.688689, 2);

But result always is the same 7... What am I doing wrong?