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 $205.40   10.556%   $227.082   $227.08   $227.10   $227.10  
  Purchase #2 $177.89   9.524%   $194.8322   $194.83   $194.85   $194.80  
  Purchase #3 $199.90   12.152%   $224.1918   $224.19   $224.20   $224.20  
  Purchase #4 $115.93   5.675%   $122.509   $122.51   $122.50   $122.50  
  Purchase #5 $236.99   10.431%   $261.7104   $261.71   $261.70   $261.70  
  Purchase #6 $240.39   10.403%   $265.3978   $265.40   $265.40   $265.40  
  Purchase #7 $206.58   11.719%   $230.7891   $230.79   $230.80   $230.80  
  7 purchase totals = $1,383.08       $1,526.5123   $1,526.51   $1,526.55   $1,526.50