Thank you so much for your response. I will try to provide information so I can get to the bottom of this, I don't want to leave this entire module in the dust.
My client ships some items individually (i.e. a box of adhesive that is approx. 53. lbs.) and some items are bundled together. I have been working directly with our local UPS Store, which my client ships through, to replicate orders he had shipped in the past to see if the weight adds up and shipping tallies correctly.
All of my weights thus far have been spot on, whether the packages were broken up or in one box. We compensated for packaging pretty accurately. I did find a few fixes in the forums for both this problem and the "won't calculate over 80 lbs." problem; nothing has worked.
Any assistance with this is greatly appreciated. Let me know if more info is needed to determine possible causes. Thanks in advance for helping me, I'm just a poor graphic designer who someone stuck a web design hat on... ;_;