You shouldn't lie during an interview, but you're under no obligation to be so openly honest by offering additional details that you do yourself a disservice getting another job. I.e. If they ask you directly "were you fired from your last job?" I'd answer "the job was challenging. Let me elaborate...", etc. and if pressed actually say you were fired. But if they don't ask you that direct question, just don't mention or allude to the fact you were fired. At least that's how I'd play it.
Incidentally the same thing applies with "what were you earning?". Always ignore the question and deflect. Answer the question you wanted to hear which is "how much do you want?" and deflect. E.g. The correct answer is "I'm looking for $xx,000. So what sort of tech are they using?". If they press you for a figure just say you don't feel it's relevant because you took that job for a variety of reasons, but you're looking to make $xx,000. If they won't let it drop walk away unless it's megacorp that you're desperate to work for. "What's the minimum we can pay you?" is the most valuable piece of information a potential employer can find out about you and the last thing you should tell them.