Explanation:
3,740,231,580
we normally start rounding from the end so the last number should be checked. If it's not more than 5, then make it a zero and move on to the next. if it's more than five, make the number zero and add 1 to the the next number. So this is how it will look.
3,740,231,580
3,740,231,580
3,740,231,590
3,740,231,600
3,740,232,000
3,740,230,000
3,740,200,000
3,740,000,000
And I think that's it