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 $248.93   5.517%   $262.6635   $262.66   $262.65   $262.70  
  Purchase #2 $205.78   8.215%   $222.6848   $222.68   $222.70   $222.70  
  Purchase #3 $82.87   4.629%   $86.7061   $86.71   $86.70   $86.70  
  Purchase #4 $32.65   12.581%   $36.7577   $36.76   $36.75   $36.80  
  Purchase #5 $70.69   8.380%   $76.6138   $76.61   $76.60   $76.60  
  Purchase #6 $83.73   4.596%   $87.5782   $87.58   $87.60   $87.60  
  Purchase #7 $228.66   4.697%   $239.4002   $239.40   $239.40   $239.40  
  7 purchase totals = $953.31       $1,012.4043   $1,012.40   $1,012.40   $1,012.50