http://www.gromacs.org/Documentation/Errors#System_has_non-zero_total_charge
"If the charge is already close to an integer, then the difference is
caused by rounding errors and not a major problem."
If want to pursue further, there are discussions and comments by
developers on this emailing list
Hi,
Running grompp I get the NOTE "System has non-zero total charge: 0.000180".
I have been running this electrolyte system which includes multiple
molecules before without a problem. There are ions in the system as well as
polar molecules (via atomic partial charges). The total charge of each