IRA savings is either trivial math (current marginal rate times IRA contribution), or it's very complex (for the large number of situations where there's some benefit with a cliff, like the Saver's credit or APTC). The situation you're talking about, where the client is on the edge of a tax bracket and wants to make the IRA contribution that saves them maximum 22% tax but no 12% tax falls into one category (look at the tax brackets and subtract) or the other (capital gains / qualified dividend rate means the number to compare to the brackets isn't obvious).

When it's complex, my method is to have the software calculate the tax with the maximum IRA deduction and with no IRA deduction, then I do the math to calculate the percentage of tax saved. If that's the current marginal rate, it's a trivial one - every dollar saves you that same percentage. If it's complex, I ask the client if they're interested in making an IRA contribution that could save them a disproportionate amount of tax - because plenty of people in that situation don't have the cash flow no matter how much tax it saves. If they're interested, I plug some intermediate numbers in for the IRA deduction and see if there's an obvious break point.

I don't think this would be a trivial item to code into the software.