Milliseconds and nanoseconds helpers

We have 3 cases

(Time.now.to_f * 1000).to_i  #milliseconds exact
(Time.now.to_f * 1000000).to_i  #nanoseconds exact
(Time.now.to_f * 1000).round(2)  #milliseconds with 2 decimals in fractions
(Time.now.to_f * 1000)  #milliseconds with fractions