Cash can be indicative of the amount of energy you are willing to commit or being asked to commit to the subject matter of the dream.
Petty cash often indicates that you do not value the subject matter of the dream. For example, to dream of a silver box with petty cash inside, says that you view intuition (silver) as petty or that the information you get that way is petty. Hardly worth sharing because it is of no real value. You need to place a far higher value on your ability.
A woman at a cash register indicates your mother placed a price on her love.