Oshkosh, WI Sales Tax Rate. The current total local sales tax rate in Oshkosh, WI is 5.000%. The December 2016 total local sales tax rate was also 5.000%. Oshkosh, WI is in Winnebago County. Oshkosh is in the following zip codes: 54901, 54902, 54903, 54904, 54906.