Round to nearest 0.50

The Mround function will do what you want.

=Mround(1.25, 0.5) returns 1.5





MROUND

Returns a number rounded to the desired multiple.


Syntax

MROUND(number,multiple)

Number   is the value to round.

Multiple   is the multiple to which you want to round number.


Remarks

MROUND rounds up, away from zero, if the remainder of dividing number
by multiple is greater than or equal to half the value of multiple.

Examples

MROUND(10, 3) equals 9

MROUND(-10, -3) equals -9

MROUND(1.3, 0.2) equals 1.4

MROUND(5, -2) equals #NUM!