In a large saucepan over high heat combine the water, cider vinegar, red wine vinegar, onion, carrot, salt, pepper, bay leaves, cloves, juniper, and mustard seeds. Cover and bring this to a boil, then lower the heat and simmer for 10 minutes. Set aside to cool.
Pat the bottom round dry and rub with vegetable oil and salt on all sides. Heat a large saute pan over high heat; add the meat and brown on all sides, approximately 2 to 3 minutes per side.
When the marinade has cooled to a point where you can stick your finger in it and not be burned, place the meat in a non-reactive vessel and pour over the marinade. Place into the refrigerator for 3 days. If the meat is not completely submerged in the liquid, turn it over once a day.
After 3 days of marinating, preheat the oven to 325 degrees F.
Add the sugar to the meat and marinade, cover and place on the middle rack of the oven and cook until tender, approximately 4 hours.
Remove the meat from the vessel and keep warm. Strain the liquid to remove the solids. Return the liquid to the pan and place over medium-high heat. Whisk in the gingersnaps and cook until thickened, stirring occasionally. Strain the sauce through a fine mesh sieve to remove any lumps. Add the raisins if desired. Slice the meat and serve with the sauce.