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 $241.56   7.724%   $260.2181   $260.22   $260.20   $260.20  
  Purchase #2 $232.67   13.479%   $264.0316   $264.03   $264.05   $264.00  
  Purchase #3 $168.99   8.253%   $182.9367   $182.94   $182.95   $182.90  
  Purchase #4 $58.90   8.182%   $63.7192   $63.72   $63.70   $63.70  
  Purchase #5 $216.41   7.274%   $232.1517   $232.15   $232.15   $232.20  
  Purchase #6 $191.87   11.612%   $214.1499   $214.15   $214.15   $214.10  
  Purchase #7 $240.91   3.251%   $248.742   $248.74   $248.75   $248.70  
  7 purchase totals = $1,351.31       $1,465.9492   $1,465.95   $1,465.95   $1,465.80