I do half the time.. But sometimes the item I need to sell cannot be sold to a specific vendor. Trading really shouldn't be this annoying.. But I didn't know I could get more gold out of them through a speech perk, thanks other person I am not replying to.

Which is why I always encourage my friends to get the Merchant perk under the Speech Tree. It allows you to sell any items to any merchants and this perk more than triples your income. If you've noticed, blacksmiths usually have the most gold among NPCs (1k+), this will accommodate adept lvl and higher robes or ebony-grade weapons. The perk only cost 3 points to get and 50 speech skill, which is relatively cheap for me. I'm not so sure about the usefulness of the Investor perk and Master Trader perk. Just with the Merchant perk, I find myself swimming in gold already, so much so I stopped picking up loot. Other than houses and training, I don't see the point of gold in this game.
Tips for selling lootBest place to sell loot will be Riften. Other than the standard blacksmith, grocer and apothecary, it features 3 other merchants in their market that carries 500-750 gold ea. I haven't seen any other market merchants that carry more than 20 gold :sadvaultboy:
Another awesome place for high-end loot ie ebony-grade and above armor or any loot that cost more than 2k is the college at winterhold. Every lecturer there provides his own lil shop (500gold) but more importantly, they provide training on specific schools of magic like Destruction, Conjuration, Restoration, Illusion, Alteration. The gold you spent on training will be in their shop where you can trade items back for. Even if you are a warrior, a few lvls in Restoration will be beneficial as well (avoid death perk). Mages will have a lot more options like doing the ritual spell quests and buying master level tomes (1k+ ea) to boost up the vendor's gold.