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 $160.81   8.226%   $174.0382   $174.04   $174.05   $174.00  
  Purchase #2 $53.36   11.612%   $59.5562   $59.56   $59.55   $59.60  
  Purchase #3 $165.61   13.566%   $188.0767   $188.08   $188.10   $188.10  
  Purchase #4 $249.84   4.659%   $261.48   $261.48   $261.50   $261.50  
  Purchase #5 $15.54   13.668%   $17.664   $17.66   $17.65   $17.70  
  Purchase #6 $129.95   4.311%   $135.5521   $135.55   $135.55   $135.60  
  Purchase #7 $56.86   3.639%   $58.9291   $58.93   $58.95   $58.90  
  7 purchase totals = $831.97       $895.2963   $895.30   $895.35   $895.40