Actually, you can tab, it's just a nuisance to do it. Start each paragraph with <p style="text-indent: 4em"> (like I did with this one), and it will indent (aka tab) the paragraph. Adjust the "4em" as desired.
However, you can't indent the paragraphs without the blank lines, because <p> automatically puts in a blank line even if you don't even use spaces around it, as this post also proves.