I am making a price list in excel. I need to do horizontal parallel
borders every 5 lines and I was wondering if there was a way to
automatically do this as opposed to manually clicking in the borders.

One way is to use conditional formatting.

First select the whole sheet and use:
Format Conditional formatting

In the resulting dialog box, use the pull-down to choose
Formula Is
and in the empty rectangle put
=MOD(ROW(),5)=0

Then click the "Format" button and in the "Border" tab select the bottom
border.

Finally, click "OK"