I have been researching on if condition, but unable to get it work,

I have to write a IF comnditon for the folowing,

Dollars Points

$3.0 1
$4.0 2
$5.0 3
$6.0 4
$7.0 5
$8.0 6
$9.0 7
$10.0 8


If $ value is =3 then 1
if $ value is =3.5 and <4 then 2
iif $ value is =4.5 and <5 then 3

like wise,

If not possible with IF condition, please let me know for alternative
formule,

please help