Ebay Shipping Costs

I can only think of one way. When you have done your search and you have a list of items, at the top right of the list is a drop-down options box labelled "sort by", which you can use to order the list. One option is "price plus P+P, lowest first".
I use this sometimes to when I am looking to buy an item which lots of sellers have listed at a similar price, but with wildly different postage charges. It will find the overall best deal.