It's BS. Stay with the number you've asked.

That's the thing. When the new company ask you about your current salary, always round it up(close to what you want). If they do background check and come back ask you (usually they dont) why you said higher than your salary, you can say, the number you gave to them is the salary + bonus + benifit(trainging, whatever)

The thing is: if they really like you , they will give you what you want on salary. dont give up.