First, copy the datalist format.
Click on a cell in the datalist and then click on the "Format Painter" icon
(yellow paintbrush) and then click in a new, empty, unused cell.
Now, in this formatted cell, key in 1.05.
Right click in this cell and choose "Copy".
Select the datalist, and right click in that selection.
Choose "Paste Special", and click on "Multiply", then <OK>, then <Esc>.
You can clear the cell containing the 1.05.