How much more 'accurate' are you expecting things?
A couple of percent looks pretty good really. There are a number of things that are going to affect the readings you get between your multimeter and the analog ports via voltage divider.
Your Arduino analog ports have 8 bit resolution. Your multimeter most likely has better than 8 bit resolution.
Your multimeter has limits. It will have accuracy fingures given in both percentage and digits (if digital).
Your reference voltage may not be exactly 5v, and will vary slightly with the load on that supply line.
Your resistors have a tolerance. Are you using 5% or 1% resistors. They will also vary as they will have a temperature coefficient.
You are measuring the resistances too, which again will be within the measuring tolerances of your meter AND at a specific temperature that can change.
Combine all of these and what you are seeing is actually pretty good as far as I can see.
You're measuring with two different instruments, in different ways, with various things that have errors and tolerances.