On a monthly basis, retail sales were decreased 1.9% from November to December (seasonally adjusted), but sales were up 16.9 percent from December 2020.
From the Census Bureau report:
Advance estimates of U.S. retail and food services sales for December 2021, adjusted for seasonal variation and holiday and trading-day differences, but not for price changes, were $626.8 billion, a decrease of 1.9 percent from the previous month, but 16.9 percent above December 2020.
This graph shows retail sales since 1992. This is monthly retail sales and food service, seasonally adjusted (total and ex-gasoline).
Retail sales ex-gasoline were down 2.0% in December.