sp. "which takes 100 readings, sums them, then divides by 101" (despite what the comment says)
Yes, because with a 32 bit IEE-754 floating point value you can expect no more than 6 or 7 significant decimals.
(Back-of-a-beermat calculation: 32 bit IEEE-754 has a mantissa of 23 bits. log10 223 = 6.924)