Excel Marco to change numbers?

I have a excel worksheet that I import numbers into from a commodity trading program. The problem I have is that the numbers that come in are in 1/8ths instead of whole numbers. For example 300.5 (half) will come in as 300.4. Is there any way to write a macro to convert all the XXX.4 to XXX.5? I need to do this for all the 1/8th. Another example 302.2 should be 302.25. XXX=.1 =XXX.125 XXX.3=XXX.375, XXX.5=XXX.625. Would it be possible to create a macro that does that? I have no programming knowledge at all and info on where to get started would be great. This worksheet has about 500 trades a day and entered them manually is a pain. thanks