one way:

=FLOOR(A1-B2,0.125)

In article ,
Jday wrote:

I ave read many publications on rounding, but can't get an answer. I know how
to round a given cell. How do you round the result of an equation to the
lowest eigth? In other words, =sum(a1-b2), where a1 is = to 3.75 and b2 is =
.05 , result (3.70), but the result should be rounded down to the next lowest
1/8th? 3.625 in the equation shown.