For taxes it's not too bad actually, you can see records in email/system and use those values. Remember they're not going to come at you for 100 bucks difference just like you are not going to die if you paid 100 excess, it is not material or significant in the grand scheme of things. Approximate values are fine there is no need for hairsplitting, just like you don't measure how much ink you used in your pen or how much you sharpened your pencils and claim 3 cents pencil devaluation in the course of business lol 😆 😜