I'm rounding number to the nearest hundredth like 6.271 is 6.371 right

No it will be 6.27 as the hundredth column is the second after the decimal place. To work out what to round it to look at the number after the hundredth column and if it is between 1 and 4, round down by just taking the number off like this, or if it is 5 to 9 round up the hundredth column by adding one to the number e. g. 5.578 would round up to 5.58.