You could do it like a standard toe shaping for a sock. Here is a link to instructions for one. You will have to adjust a little about numbers of stitches based on what you have. SILVER'S SOCK CLASS
Then down at the bottom of the page is a link to the final step of grafting the toe closed.
That kind of toe would put the toe in one place like a regular sock. If you don't want that for your tube sock you could shape it like you do the top of a hat putting as many decreases as you want on each decrease round, and decreasing as fast as you want. For instance get your number of stitches to something that will evenly divide by what you want to work with, for instance 10. Knit 8 and knit sts 9 and 10 together. Then put one stitch less between decreases in the decrease rows each time. Hats often decrease every other row, with an even row between. But you can do whatever you want, just keep track so you can duplicate it on the other sock.