I've found a glitch that can completely ignore the time from the final death cutscene and the rabbits. In order to cut about 14 seconds from your final time, you must be at one health at the end of the final stage, and die right as you collect the last damage tile. You will go to the death screen for losing all your hearts, but it won't center the player and health bar like usual. Don't go back to menu, just wait, and the boss will die in the background, rabbits and all, the congrats screen will play, and it wont have counted any time from the whole time you were dead. I have a video of me doing it here:

https://drive.google.com/file/d/1ClzZyEC1GsGTObFCD1L5x-EvW4lAwjpV/view

watch from about 4 minutes to the end, and you'll see what I'm describing. The cards stage Is by far the easiest place to get the glitch. One of the only ways to get the glitch is to be right above or below the damage tile, and move up or down onto the tile as a card flies over it.