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 $60.27   4.727%   $63.119   $63.12   $63.10   $63.10  
  Purchase #2 $249.78   4.770%   $261.6945   $261.69   $261.70   $261.70  
  Purchase #3 $147.76   9.206%   $161.3628   $161.36   $161.35   $161.40  
  Purchase #4 $206.27   12.178%   $231.3896   $231.39   $231.40   $231.40  
  Purchase #5 $74.60   9.597%   $81.7594   $81.76   $81.75   $81.80  
  Purchase #6 $101.31   13.732%   $115.2219   $115.22   $115.20   $115.20  
  Purchase #7 $236.88   4.335%   $247.1487   $247.15   $247.15   $247.10  
  7 purchase totals = $1,076.87       $1,161.6959   $1,161.69   $1,161.65   $1,161.70