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 $83.46   13.459%   $94.6929   $94.69   $94.70   $94.70  
  Purchase #2 $149.98   7.802%   $161.6814   $161.68   $161.70   $161.70  
  Purchase #3 $247.48   7.516%   $266.0806   $266.08   $266.10   $266.10  
  Purchase #4 $238.32   3.527%   $246.7255   $246.73   $246.75   $246.70  
  Purchase #5 $239.51   9.339%   $261.8778   $261.88   $261.90   $261.90  
  Purchase #6 $223.78   10.182%   $246.5653   $246.57   $246.55   $246.60  
  Purchase #7 $237.70   7.798%   $256.2358   $256.24   $256.25   $256.20  
  7 purchase totals = $1,420.23       $1,533.8593   $1,533.87   $1,533.95   $1,533.90