This thread is more suitable for sci.electronics, but here's my 2 cents
worth:

I don't think a program to pick ratios of 1% (E96 range) components is
all that useful: if you're at that level of precision then stick a
trimmer in and be done with it.  [The trimmer costs 20 cents and the
label saying "Warning! Do not adjust this trimmer!" costs another 20c.
But that cost is inevitably recovered: the customer pays for service
after he adjusts the trimmer in spite of all the good advice.:-]

However, for E12 and E24 ranges there is some justification.  For a
start, 1% components are much easier to get in the E12/E24 range so
it is useful to be able to pick the optimum values when 5/10% just isn't
good enough.  Secondly, resistors are manufactured to a much tighter
tolerance than their nominal rating.  I have measured many 5% res and
found that they are almost all within 1%.  Nominal 1% res come in under
0.5%.  It seems that the manufacturers build in a little extra precision
to account for aging, temperature variations etc.  Resistors from the
same batch are almost identical, which is a boon if you are making
instrumentation amps etc.

Regards,
SJH
Canberra, Australia