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 $179.36   8.822%   $195.1831   $195.18   $195.20   $195.20  
  Purchase #2 $32.74   5.209%   $34.4454   $34.45   $34.45   $34.40  
  Purchase #3 $222.46   6.309%   $236.495   $236.50   $236.50   $236.50  
  Purchase #4 $250.69   4.307%   $261.4872   $261.49   $261.50   $261.50  
  Purchase #5 $152.65   11.403%   $170.0567   $170.06   $170.05   $170.10  
  Purchase #6 $184.60   13.594%   $209.6945   $209.69   $209.70   $209.70  
  Purchase #7 $87.75   13.266%   $99.3909   $99.39   $99.40   $99.40  
  7 purchase totals = $1,110.25       $1,206.7528   $1,206.76   $1,206.80   $1,206.80