The ornamental design for a toilettissueholder, as shown and described.
FIG. 1 is a top, front, and left perspective view of a toilet tissue holder showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is an additional is a top, front, and left perspective view thereof, with the broken-line disclosure being for illustrative purposes only and forming no part of the claimed design.