How to improve an if/else function in a jQuery game?

I wrote a little jQuery rock/paper/scissors/lizard/spock game and when the user clicks the button to make their choice from the five options, I choose the computer's randomly, and then compare the two to find a winner and output the result. It works, but I have the feeling that the findWinner function can be a lot shorter or more elegant. I'm trying to improve my Javascript and jQuery, and was hoping for someone to help me with next steps here:

This is how I'm doing it:

function findWinner(choiceA,choiceB) {
  if (choiceA == choiceB) {
    return "It's a tie!"; 
  }

  if (choiceA == 'Rock') {
    if (choiceB == 'Lizard' || choiceB == 'Scissors') {
      return "You win!";
    }
    else if (choiceB == 'Spock' || choiceB == 'Paper') {
      return choiceB;
    }
  }
  else if (choiceA == 'Paper') {
    if (choiceB == 'Rock' || choiceB == 'Spock') {
      return "You win!";
    }
    else if (choiceB == 'Scissors' || choiceB == 'Lizard') {
      return "Computer wins :( "; 
    }
  }
  else if (choiceA == 'Scissors') {
    if (choiceB == 'Paper' || choiceB == 'Lizard') {
      return "You win!";
    }
    else if (choiceB == 'Spock' || choiceB == 'Rock') {
      return "Computer wins :( "; 
    }
  }
  else if (choiceA == 'Lizard') {
    if (choiceB == 'Paper' || choiceB == 'Spock') {
      return "You win!";
    }
    else if (choiceB == 'Rock' || choiceB == 'Scissors') {
      return "Computer wins :( "; 
    }
  }
  else if (choiceA == 'Spock') {
    if (choiceB == 'Rock' || choiceB == 'Scissor') {
      return "You win!";
    }
    else if (choiceB == 'Paper' || choiceB == 'Lizard') {
      return "Computer wins :( "; 
    }
  }
}

This just seems very repetitive, but I'm not sure where to go next with it.

Thanks!