Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $214.49   3.565%   $222.1366   $222.14   $222.15   $222.10  
  Purchase #2 $216.94   3.394%   $224.3029   $224.30   $224.30   $224.30  
  Purchase #3 $55.29   9.362%   $60.4662   $60.47   $60.45   $60.50  
  Purchase #4 $61.59   10.343%   $67.9603   $67.96   $67.95   $68.00  
  Purchase #5 $114.72   5.429%   $120.9481   $120.95   $120.95   $120.90  
  Purchase #6 $235.25   6.528%   $250.6071   $250.61   $250.60   $250.60  
  Purchase #7 $83.38   13.443%   $94.5888   $94.59   $94.60   $94.60  
  7 purchase totals = $981.66       $1,041.0100   $1,041.02   $1,041.00   $1,041.00