How is the roman number system like the us number system?

It is not because the US number system is based on the Hindu-Arabic numeral system of: 1 2 3 4 5 6 7 8 9 and 0

Whereas the equivalent Roman numerals are: I II III IV V VI VII VIII IX and N

There are Roman numerals on the back of a dollar bill which are MDCCLXXVI and they represent 1776