How can I round values?

Make own one. You can truncate to integer using .toNumber().
You can this use to made round function, look example:

//trunc(a,1)
var a=9.67;
var b=(a*10).toNumber().toFloat()/10;
// b=9.6

//round(a,1)
var a=9.67;
var b=(a*10+0.5).toNumber().toFloat()/10;
// b=9.7

//round(a,2)
var a=9.673;
var b=(a*100+0.05).toNumber().toFloat()/100;
// b=9.67

Watch to negative!