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 $184.94   5.583%   $195.2652   $195.27   $195.25   $195.30  
  Purchase #2 $117.27   4.260%   $122.2657   $122.27   $122.25   $122.30  
  Purchase #3 $242.67   6.276%   $257.9   $257.90   $257.90   $257.90  
  Purchase #4 $163.90   7.158%   $175.632   $175.63   $175.65   $175.60  
  Purchase #5 $171.35   8.863%   $186.5368   $186.54   $186.55   $186.50  
  Purchase #6 $157.46   4.359%   $164.3237   $164.32   $164.30   $164.30  
  Purchase #7 $234.47   9.480%   $256.6978   $256.70   $256.70   $256.70  
  7 purchase totals = $1,272.06       $1,358.6212   $1,358.63   $1,358.60   $1,358.60