The ornamental design for a tanktop, as shown and described.
FIG. 1 is a front perspective view of a tank top showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof; and,
FIG. 5 is an enlarged view of the identified region labeled by the numeral “5” in FIG. 1.
The broken line showing of the zipper within the shaded area forms no part of the claimed design. In FIG. 5, the line shading is used to represent the appearance of the ribbing and no particular material, texture, or contrast is hereby claimed. The broken lines immediately adjacent to the shaded area define the bounds of the claimed design and form no part thereof. The broken lines depicting the remainder of the tank top show features that form no part of the claimed design.