There is no obligation to tip in Switzerland because service is included in restaurants, bars and hotels, etc. Rounding to the next Swiss franc for small amounts or giving a couple of Swiss francs, up to 5 percent, when spending larger amounts in expensive restaurants is usual.
As giving a tip is not expected, when it does happen it’s seen as confirmation of good service.
Although tax and a tip are already in the price of hiring a taxi, usually the driver will round up the fare to the nearest Franc.