Paying your taxes can be a real bummer, but the plethora of special Tax Day promotions and giveaways on deck will hopefully brighten moods in Washington today. For those of you able to be near the IRS Building (10th and Pennsylvania) from noon to 1 p.m., you’ll be able to get a free 6 oz. Blizzard from the Dairy Queen’s Blizzard mobile. A number of local restaurants are also offering Tax Day promotions: >>…