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 $54.69   7.345%   $58.707   $58.71   $58.70   $58.70  
  Purchase #2 $201.81   6.128%   $214.1769   $214.18   $214.20   $214.20  
  Purchase #3 $196.30   4.556%   $205.2434   $205.24   $205.25   $205.20  
  Purchase #4 $34.44   10.396%   $38.0204   $38.02   $38.00   $38.00  
  Purchase #5 $126.55   13.543%   $143.6887   $143.69   $143.70   $143.70  
  Purchase #6 $239.70   8.537%   $260.1632   $260.16   $260.15   $260.20  
  Purchase #7 $82.70   13.844%   $94.149   $94.15   $94.15   $94.10  
  7 purchase totals = $936.19       $1,014.1486   $1,014.15   $1,014.15   $1,014.10