Did the same thing when I was working at Target during high school. I wasnt a full time cashier but when I did cashier I made sure to be efficient. I dont think I ever called on a manager (well once but thats because some lady had every card and even her checks come back as not accepted then she proceeded to yell at me and then start throwing bags of merchandise over the counter at me) but working on the sales floor most of the time I knew the price for most stuff so if an item did not scan I automatically deducted about 50-75% off the retail price and asked the customer if that seemed fair (no one ever said no) and went about my business. Oh yeah if a clothing item came up with no price I priced it at $1.99 unless it looked cheaper than $1.99 in which case it was $0.49. Im sure I made the store lose some cash but I didnt care I hated the job and they never reprimanded me for what I did.