How to create a formula to add a markup price

I have an array of single column with multiple rows formatted as numbers.
In my file, it’s P1 onwards.

I can’t create another row/column, since this file is from an exported file and later on be uploaded for database import.

In my real-world application, these numbers are product prices.
Now I’d like to add a markup of 5% on top of the currently entered prices.
So my formula would be,

my total markup price = current entered price + (0.005*currently-entered-price)

UPDATE:

Based on the accepted answer below and from linked page, I don’t need to create a formula. I just needed to put 1.05 (100% + 5%) to some empty cell, and then copy it, and high-light or select the cells/items that I need to update, then right-click > paste special > select multiply. Boom! Done!

Refer this answer about using paste special to multiply a range by another value. You will want to multiple by 1.05 to give a 5% increase.

That was awesome! Oh, I love that one!