What you are missing is that for taxable income under $100,000 you cannot use the bracket percentages to calculate your tax. You have to use the Tax Table. The Tax Table works in small steps. In the Tax Table, for taxable income of $70,150 to $70,199, for married filing jointly, the tax is $7,967. TurboTax is following the IRS rules for calculating the tax.
CORRECTION: The tax in the Tax Table is $7,957, not $7,967.
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