Wow! I'll be impressing DH with that trivia when we are there! Thanks
Yeah I can't imagine anything else! You guys must get really good at calculating percentages in your head!
Thank you both so much for your help
If you want the nitty gritty, ping Cheshire Figment. He's a former accountant and knows all the reasons why. Be warned, he IS a former accountant though

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As far as the percentages, most people just round. Here in Mobile, we had a 10% tax rate (an additional 1% tax recently expired, so now it's 9%) which made things quite easy. If it was $2.00, it's now $2.20! I typically still use 10% to estimate the cost of stuff here, and even down there if I have to. Simply because it's easy, and I find it better to over budget than under. Of course, if I have a few extra minutes, I'll get something closer to the real cost, but I am better with numbers than your average person.
We recently (last Friday night) found the price of the BOMA dinner buffet to be incorrect. Allearsnet posted the price of $39.99! It almost discouraged us from going but it's a family favorite. Imagine my surprise when the check for a party of 5 adults was $165 give or take a few cents; around $33 per person. YAY!
Yep, many of the buffet menus at AllEars include the seasonal upcharges and then mentions that "Additional seasonal upcharges may apply" (well, not those exact words, but you get the idea). It drives me crazy that they can't keep it consistent even within the site.
At least for budgeting reasons, you should always assume that the price is before upcharge and tax, giving you a higher number to budget for. If it's less, great, but you'll be far less likely to be charged more than the budget.