In that case there would be no inflation or deflation, assuming a fixed money supply and no economic growth. However, the the key here is that the government, the federal government anyways, is spending money regardless of the tax break. Anytime the government writes a check, that's a little bit more money floating around; anytime the government collects some money, such as taxes, there's that much less money to be had. Every tax break causes the money supply to increase more relative to if the tax break did not exist, causing more inflation (or less deflation, if that were the case). If the government spent exactly as much as it taxed, then there would be... actually deflation, because the economy is growing. This is the basics of fiscal policy.

There's also the monetary policy, which is when the federal reserve does this on purpose. The general principle is the same, but instead it spends its money buying bonds and gets its money selling those bonds, and creates a bunch of rules about where banks keep their money so it always has some money on hand.