Here is why they won't work.
Traditional (including 3D) scanners with lasers work by bouncing the laser off the barcode, and reading what is returned. It's pure 1s and 0s. Light on, light off. Black bounces back less light. Someone will ask why this won't work scanning a screen, that still has black and white? Quite simple. The scanner is attuned to the specific wavelength of the laser. It cannot read the screen because it isn't the same red wavelength. The laser will bounce back equally across the entire display, because the glass will look like a mirror to it. There is no differentiation of light, so no light on light off effect. No 1s and 0s.
More recently, barcode scanners have been implementing optical cameras, that work much the same way as a QR reader on your phone would. It takes a look at the image, and is smart enough to figure out the orientation and then read the information from it. Some of these will even look so much like the traditional scanner that they will have lasers they use, but it is for the operator to know they have aligned the barcode in the right spot for the camera to see the code.
So... Long story short, any store that uses a traditional laser barcode scanner will not be able to read anything off your phone. Any store with an optical scanner, even if it shoots laserbeams from its forehead, will have no problem reading the code from your phone.