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 $57.49   3.437%   $59.4659   $59.47   $59.45   $59.50  
  Purchase #2 $237.51   10.174%   $261.6743   $261.67   $261.65   $261.70  
  Purchase #3 $67.59   3.464%   $69.9313   $69.93   $69.95   $69.90  
  Purchase #4 $69.67   6.110%   $73.9268   $73.93   $73.95   $73.90  
  Purchase #5 $213.31   8.412%   $231.2536   $231.25   $231.25   $231.30  
  Purchase #6 $225.56   10.463%   $249.1603   $249.16   $249.15   $249.20  
  Purchase #7 $180.37   9.569%   $197.6296   $197.63   $197.65   $197.60  
  7 purchase totals = $1,051.50       $1,143.0418   $1,143.04   $1,143.05   $1,143.10