When mining, all my shares are rejected. Why am I not getting any accepted shares? This applies for when I mine anything (Litecoins, Dogecoin, etc.) I have a Radeon HD 6670 (mining @ 100 Mh/s according to cgminer) and it isn't overclocked or anything. Kind of puzzled as to why this is happening. 

Does anyone know why I am not able to mine successfully?
My guess is that you did not launch cgminer with the --scrypt option.  This is required to mine Litecoin, Dogecoin or any other scrypt coin. When mining scrypt coins that card should deliver ~100 Kh/s in your screen shot it shows Mh/s which would indicate that you are using SHA256 which is for Bitcoin.