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 $164.47   6.357%   $174.9254   $174.93   $174.95   $174.90  
  Purchase #2 $63.92   10.225%   $70.4558   $70.46   $70.45   $70.50  
  Purchase #3 $51.47   7.156%   $55.1532   $55.15   $55.15   $55.20  
  Purchase #4 $87.84   6.369%   $93.4345   $93.43   $93.45   $93.40  
  Purchase #5 $102.74   10.857%   $113.8945   $113.89   $113.90   $113.90  
  Purchase #6 $220.34   5.520%   $232.5028   $232.50   $232.50   $232.50  
  Purchase #7 $13.34   9.241%   $14.5727   $14.57   $14.55   $14.60  
  7 purchase totals = $704.12       $754.9389   $754.93   $754.95   $755.00