Numbers 5 and over round up to the nearest 10. Numbers like 164 would found to the nearest 10 of 160 because the last number (unit) is below 5, so it rounds down. I hope this helps but you can find tutorials on google good luck!
When you round to the nearest 10 you look at the ones place and see if it is greater or less than 5. If it is greater you round up if less than you leave it the same. For 100 you look at the 10s place and you do the same thing
