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 $60.72   5.220%   $63.8896   $63.89   $63.90   $63.90  
  Purchase #2 $56.88   6.331%   $60.4811   $60.48   $60.50   $60.50  
  Purchase #3 $87.65   7.822%   $94.506   $94.51   $94.50   $94.50  
  Purchase #4 $121.69   6.136%   $129.1569   $129.16   $129.15   $129.20  
  Purchase #5 $41.41   5.266%   $43.5907   $43.59   $43.60   $43.60  
  Purchase #6 $246.25   7.863%   $265.6126   $265.61   $265.60   $265.60  
  Purchase #7 $78.58   11.533%   $87.6426   $87.64   $87.65   $87.60  
  7 purchase totals = $693.18       $744.8795   $744.88   $744.90   $744.90