The ornamental design for a multipurpose round basket, as shown and described.
FIG. 1 is a plan view illustration of the multipurpose round basket of the ornamental design;
FIG. 2 is a bottom view illustration of the multipurpose round basket of the ornamental design; and,
FIG. 3 is a side elevational view illustration of the multipurpose round basket of the ornamental design, the opposite elevational view thereof being identical therewith.