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 $62.95   12.798%   $71.0063   $71.01   $71.00   $71.00  
  Purchase #2 $36.95   8.117%   $39.9492   $39.95   $39.95   $39.90  
  Purchase #3 $250.29   5.357%   $263.698   $263.70   $263.70   $263.70  
  Purchase #4 $70.30   8.628%   $76.3655   $76.37   $76.35   $76.40  
  Purchase #5 $133.84   12.735%   $150.8845   $150.88   $150.90   $150.90  
  Purchase #6 $79.34   10.837%   $87.9381   $87.94   $87.95   $87.90  
  Purchase #7 $63.81   8.683%   $69.3506   $69.35   $69.35   $69.40  
  7 purchase totals = $697.48       $759.1922   $759.20   $759.20   $759.20