I have the opportunity to sell an odd lot of company stock I have at a low fee. How would I decide if it makes sense for me to do so?

If you sold this thru a broker then they will be issuing a form 1099-B in February ... use the info on that form to enter the sale in the investment section of the interview. 

who is holding your odd lot?

The fee of $125 is not a low fee.

If you transfer the holding to an actual no-commission broker, you can then sell it, now or later for no commission.

There's nothing wrong with holding odd lots or fractional shares.

Lots of investors have odd lots because companies rarely split their stock nowadays so price per share is high.

You may reduce the amount you receive from selling your stock by the amount of your transaction fee, thus reducing your taxable capital gain.

Whether or not you should actually proceed with the sale is a personal decision.