Smaller Bills

I am starting to loose my cool everytime I go to a local store. Whether it's a small ice cream stall or a giant grocery store the cashier always ask if I have a smaller bill. For example I went to a department store yesterday to purchase a can opener for P49.75. I gave the cashier P100 and immediately she gave me a frustrated look and uttered the dreaded ”Sir, do you have a smaller bill?” What the? Well if I did I would but I don't so stop asking. It's not like I paid a P1000 bill for a P49.75 item. The asking part is really not the worse. It's more of the look and the bad vibe that they throw at you. As if making me feel that I just made their job harder.