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 $69.77   5.533%   $73.6304   $73.63   $73.65   $73.60  
  Purchase #2 $78.76   4.180%   $82.0522   $82.05   $82.05   $82.10  
  Purchase #3 $219.45   4.381%   $229.0641   $229.06   $229.05   $229.10  
  Purchase #4 $164.42   6.571%   $175.224   $175.22   $175.20   $175.20  
  Purchase #5 $68.74   11.604%   $76.7166   $76.72   $76.70   $76.70  
  Purchase #6 $171.81   6.698%   $183.3178   $183.32   $183.30   $183.30  
  Purchase #7 $121.83   10.600%   $134.744   $134.74   $134.75   $134.70  
  7 purchase totals = $894.78       $954.7491   $954.74   $954.70   $954.70