First of all, I'd find a way to buy online to avoid sales tax, or move to/buy at another locale with a lower tax rate.
Item retails for 'X'
At checkout, the tax is added at 12.5% of 'X'
Thus you are paying 1.125X, which is the stated $30. Equation would be:
1.125X = 30
or
X = 30/1.125 = $26.67 (actually $26.66666666...); but all depends on the tax charting for the range around $26.66 and $26.67
