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 $23.28   7.189%   $24.9536   $24.95   $24.95   $25.00  
  Purchase #2 $182.87   9.431%   $200.1165   $200.12   $200.10   $200.10  
  Purchase #3 $228.59   7.863%   $246.564   $246.56   $246.55   $246.60  
  Purchase #4 $237.27   11.294%   $264.0673   $264.07   $264.05   $264.10  
  Purchase #5 $244.72   8.546%   $265.6338   $265.63   $265.65   $265.60  
  Purchase #6 $55.65   11.388%   $61.9874   $61.99   $62.00   $62.00  
  Purchase #7 $102.66   12.223%   $115.2081   $115.21   $115.20   $115.20  
  7 purchase totals = $1,075.04       $1,178.5307   $1,178.53   $1,178.50   $1,178.60