We should include sales tax in the initial price of products

Why isn’t it the law to add sales tax to the intial price of any product? It’s so stupid to me. Every time I go shopping I try to calculate how much I’m spending but it’s basically impossible with the addition of sales tax. I feel like it also creates a mentality that ‘the government is taking our money’ by making us see the price increase every time we pay at the cashier. Life would be so much simpler, and honestly, I feel like it falsely deludes people into thinking they’ll spend less money. I don’t see why we do this.