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 $118.80   5.705%   $125.5775   $125.58   $125.60   $125.60  
  Purchase #2 $235.29   12.387%   $264.4354   $264.44   $264.45   $264.40  
  Purchase #3 $130.37   8.104%   $140.9352   $140.94   $140.95   $140.90  
  Purchase #4 $131.29   7.583%   $141.2457   $141.25   $141.25   $141.20  
  Purchase #5 $249.59   4.312%   $260.3523   $260.35   $260.35   $260.40  
  Purchase #6 $217.49   5.112%   $228.6081   $228.61   $228.60   $228.60  
  Purchase #7 $179.40   8.365%   $194.4068   $194.41   $194.40   $194.40  
  7 purchase totals = $1,262.23       $1,355.5610   $1,355.58   $1,355.60   $1,355.50