When rounding decimals, look at the digit after the rounding digit. For example, if rounding to the tenths place, look to the digit in the hundredths place. If that digit is $0,1,2,3,$ or $4,$ round down, and if it's $5,6,7,8,$ or $9,$ round up. See the following examples when rounding to one decimal.

Number	$\approx$
$2.21$	$2.2$
$2.25$	$2.3$
$3.99$	$4.0$