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 $214.59   10.477%   $237.0726   $237.07   $237.05   $237.10  
  Purchase #2 $149.25   4.851%   $156.4901   $156.49   $156.50   $156.50  
  Purchase #3 $48.39   4.482%   $50.5588   $50.56   $50.55   $50.60  
  Purchase #4 $35.63   3.368%   $36.83   $36.83   $36.85   $36.80  
  Purchase #5 $137.80   12.459%   $154.9685   $154.97   $154.95   $155.00  
  Purchase #6 $247.90   5.265%   $260.9519   $260.95   $260.95   $261.00  
  Purchase #7 $196.88   5.119%   $206.9583   $206.96   $206.95   $207.00  
  7 purchase totals = $1,030.44       $1,103.8302   $1,103.83   $1,103.80   $1,104.00