The state’s tax changes began going into effect July 1.Tennessee decreased its sales tax rate on groceries from 5 percent to 4 percent, while increasing its gas tax rate by 6 cents – from 21.4 cents per gallon to 27.4 cents per gallon by 2019. The bulk of the increase goes into effect this year with a 4-cent increase, followed by 1-cent increases in the subsequent years.Like gas doesn’t cost enough? Every time I fill up my car, I about have a slight panic attack.