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 $166.94   9.597%   $182.9612   $182.96   $182.95   $183.00  
  Purchase #2 $180.87   6.839%   $193.2397   $193.24   $193.25   $193.20  
  Purchase #3 $149.83   5.611%   $158.237   $158.24   $158.25   $158.20  
  Purchase #4 $112.90   5.281%   $118.8622   $118.86   $118.85   $118.90  
  Purchase #5 $49.41   7.682%   $53.2057   $53.21   $53.20   $53.20  
  Purchase #6 $157.56   4.636%   $164.8645   $164.86   $164.85   $164.90  
  Purchase #7 $136.66   12.859%   $154.2331   $154.23   $154.25   $154.20  
  7 purchase totals = $954.17       $1,025.6034   $1,025.60   $1,025.60   $1,025.60