Okay. To find the percent of change, you have to set up a proportion and set it up like this: change/original = x/100. The change is the difference between the numbers. 5.30 - 5.00 is 0.30. The amount of change is 30 cents (0.30). The original price was $5.00. Now let's set up the proportion. 0.30/5.00 = x/100. Cross multiply the values in order to get 30 = 5x. Now, divide each side by 5 to isolate the "x". When you do that, you get x = 6. There. The tax rate is 6%.