I have this same need. The <p>paragraph text</p> approach works great. So does </br></br>paragraph text</br></br>, but all of these tags are stripped out of the post after you switch back and forth between HDML view and Visual view and/or save the post once or twice. The result is that these fixes become temporary.
I tried adding li p { margin-left:0; } to my Theme CSS file but it still removes these tags.
What do you have to do to get these “foreign” tags to stick permanently?
Thanks.