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 $29.25   10.655%   $32.3666   $32.37   $32.35   $32.40  
  Purchase #2 $237.37   10.587%   $262.5004   $262.50   $262.50   $262.50  
  Purchase #3 $157.26   10.624%   $173.9673   $173.97   $173.95   $174.00  
  Purchase #4 $53.36   5.600%   $56.3482   $56.35   $56.35   $56.30  
  Purchase #5 $231.94   12.811%   $261.6538   $261.65   $261.65   $261.70  
  Purchase #6 $30.50   10.767%   $33.7839   $33.78   $33.80   $33.80  
  Purchase #7 $189.39   13.155%   $214.3043   $214.30   $214.30   $214.30  
  7 purchase totals = $929.07       $1,034.9245   $1,034.92   $1,034.90   $1,035.00