I have about seventy letters I need to send, all of which fall under Royal Mail's "Large Letter" definition.

I've weighed them on my electronic (baking) scales and they weigh 95g apparently - weight limit is 100g.

If I send these out and (due to inaccuracy of electronic scales) they actually turn out to be 105g or something, is everyone going to end up paying a surcharge? Or are the Royal Mail happy to cut their users a little slack?

Basically, I can't be arsed going to the post office and want to avoid this if possible...