complex rounding decimals in excel spreadsheet - excel

Question

Have created formula for example =(E2+(G2*37))/290 which returns decimals based on data entered but can't work out how to round the answer to get the following:
If 0 to 0.39 round to 0
If 0.4 to 0.89 round to 0.5
If 0.9 to 1.39 round to 1
If 1.4 to 1.89 round to 1.5
If 1.9 to 2.39 round to 2 etc
Hope my question makes sense. Thanks

Answer 1

Your custom rounding is simply rounding to the nearest 0.5.....but with an "offset" of 0.15. With value to be rounded in A1 you can do that with a simple formula, i.e.
=ROUND(A1*2-0.3,0)/2
or with your calculation in place of A1 that becomes
=ROUND((E2+G2*37)/290*2-0.3,0)/2

Answer 2

It's a bit convoluted but this should work:
=IF(A1 + 0.1 - ROUNDDOWN(A1+0.1;0) < 0.5; ROUNDDOWN(A1+0.1;0); ROUNDDOWN(A1+0.1;0) + 0.5)
where A1 is the cell you want to round.
e.g.
N.B.
This works only for positive numbers.
Ranges are actually:
[0, 0.39999999...] [0.4 , 0.8999999...] ...
or equally:
[0, 0.4) [0.4 , 0.9) ...

Answer 3

You could define a VBA function to do this for you:
Public Function CustomRound(number As Double)
Dim result As Double, fraction As Double
fraction = number - Int(number)
If number <= 0.39 Then
result = 0
ElseIf fraction >= 0.4 And fraction <= 0.9 Then
result = Int(number) + 0.5
Else
result = Round(number, 0)
End If
CustomRound = result
End Function
You would call this as follows:
=CustomRound((E2+(G2*37))/290)
Example:
=CustomRound(0.23) // 0
=CustomRound(1.58) //1.5
=CustomRound(2.12) //2