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 $24.82   4.820%   $26.0163   $26.02   $26.00   $26.00  
  Purchase #2 $116.55   8.716%   $126.7085   $126.71   $126.70   $126.70  
  Purchase #3 $103.84   13.389%   $117.7431   $117.74   $117.75   $117.70  
  Purchase #4 $200.34   6.663%   $213.6887   $213.69   $213.70   $213.70  
  Purchase #5 $119.68   13.574%   $135.9254   $135.93   $135.95   $135.90  
  Purchase #6 $138.79   5.837%   $146.8912   $146.89   $146.90   $146.90  
  Purchase #7 $79.82   8.513%   $86.6151   $86.62   $86.60   $86.60  
  7 purchase totals = $783.84       $853.5883   $853.60   $853.60   $853.50