This question is asked to explore the candidate's self-awareness and motivation. Know your strengths in the sales process as these will translate into what you like. Your "likes" and strengths should correspond to the main priorities of this sales position.
For example, if your strength is negotiating, describe how you enjoy this aspect of sales and your satisfaction at coming up with win-win solutions. Highlight how this has resulted in both satisfied customers and increased sales which is what this position is looking for.
When responding to the "dislikes" go carefully! The best approach is to choose a characteristic of your present or previous company such as its poor delivery on the sales you made or its lack of flexibility when it came to negotiating sales solutions. Answer in a positive manner as someone who is able to take these sort of problems in their stride and constructively improve on them.
For example if the delivery of company products was slow and resulted in angry customers, discuss how you instituted a follow-up process that accelerated delivery.