Rounding in MS Access

Be careful, the VBA Round function uses Banker's rounding, where it rounds .5 to an even number, like so:

Round (12.55, 1) would return 12.6 (rounds up) 
Round (12.65, 1) would return 12.6 (rounds down) 
Round (12.75, 1) would return 12.8 (rounds up)   

Whereas the Excel Worksheet Function Round, always rounds .5 up.

I've done some tests and it looks like .5 up rounding (symmetric rounding) is also used by cell formatting, and also for Column Width rounding (when using the General Number format). The 'Precision as displayed' flag doesn't appear to do any rounding itself, it just uses the rounded result of the cell format.

I tried to implement the SymArith function from Microsoft in VBA for my rounding, but found that Fix has an error when you try to give it a number like 58.55; the function giving a result of 58.5 instead of 58.6. I then finally discovered that you can use the Excel Worksheet Round function, like so:

Application.Round(58.55, 1)

This will allow you to do normal rounding in VBA, though it may not be as quick as some custom function. I realize that this has come full circle from the question, but wanted to include it for completeness.

In Switzerland and in particulat in the insurance industry, we have to use several rounding rules, depending if it chash out, a benefit etc.

I currently use the function

Function roundit(value As Double, precision As Double) As Double
    roundit = Int(value / precision + 0.5) * precision
End Function

which seems to work fine

Int and Fix are both useful rounding functions, which give you the integer part of a number.

Int always rounds down - Int(3.5) = 3, Int(-3.5) = -4

Fix always rounds towards zero - Fix(3.5) = 3, Fix(-3.5) = -3

There's also the coercion functions, in particular CInt and CLng, which try to coerce a number to an integer type or a long type (integers are between -32,768 and 32,767, longs are between-2,147,483,648 and 2,147,483,647). These will both round towards the nearest whole number, rounding away from zero from .5 - CInt(3.5) = 4, Cint(3.49) = 3, CInt(-3.5) = -4, etc.

To expand a little on the accepted answer:

"The Round function performs round to even, which is different from round to larger."
--Microsoft

Format always rounds up.

  Debug.Print Round(19.955, 2)
  'Answer: 19.95

  Debug.Print Format(19.955, "#.00")
  'Answer: 19.96

ACC2000: Rounding Errors When You Use Floating-Point Numbers: http://support.microsoft.com/kb/210423

ACC2000: How to Round a Number Up or Down by a Desired Increment: http://support.microsoft.com/kb/209996

Round Function: http://msdn2.microsoft.com/en-us/library/se6f2zfx.aspx

How To Implement Custom Rounding Procedures: http://support.microsoft.com/kb/196652