Dollar Tree review: short changed by cashier, refund due

On September 1, 2015, approximately at 1:30, afternoon, I purchased a box of peppermint candy for $1.07 cents .I gave the cashier a twenty dollar bill. She counted out the change at thirteen dollars and 93 cents. I realized when I went out it should have been $18.93 cents. I went back in and told her and showed the receipt. She said she remembered counting it at $13.93, but would not pay me the five dollars she owed me. I talked to the manager who said to count the drawer . She opened it and walked away leaving the cashier to count the drawer. There was no money over, but yet she still admitted to the manager she counted me out $13.93.No one cared, so I am still shorted $5.00. So did she pocket the money or what. I went back in later to tell them it was their responsibility to pay me back and do what was right, only to be rudely addressed by manager, Julie and cashier, that it was my problem. Five dollars may not be a lot to this company, but it is the principal and my integrity that is being questioned. And five dollars is a lot to me! I would appreciate it if you would address the situation and do what is right(give back my five dollars) or I will write to the CEO of the company.
Thank You,
Judith Plough
601 Reid Street
Connersville, Ind. 47331