Look at the digit in the hundredths place.
If the hundredths digit is 0–4, keep the tenths digit the same.
If the hundredths digit is 5–9, increase the tenths digit by 1.
Drop all digits after the tenths place.
Example: 3.141 → 3.1
Example: 3.149 → 3.1
Example: 3.156 → 3.2
Example: 0.05 → 0.1
Example: 12.999 → 13.0