Ask for $30 (or $10 or $60 or $600, or however much you want to search) in pennies. Say that you will take rolls, boxes, bags, loose, or whatever is convenient for them. A practical way to ask is "I would like as many pennies as you can spare up to $125 - rolls, bags, or loose).
If you are given a box of new shield Lincolns, it is OK to ask if they have any circulated ones instead. If not, take what they give you and be gracious about it. That will happen on occasion. Just dump them as usual and try your luck elsewhere.