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 $62.95   13.692%   $71.5691   $71.57   $71.55   $71.60  
  Purchase #2 $69.60   4.246%   $72.5552   $72.56   $72.55   $72.60  
  Purchase #3 $177.63   6.238%   $188.7106   $188.71   $188.70   $188.70  
  Purchase #4 $78.28   3.466%   $80.9932   $80.99   $81.00   $81.00  
  Purchase #5 $121.80   13.757%   $138.556   $138.56   $138.55   $138.60  
  Purchase #6 $168.81   4.602%   $176.5786   $176.58   $176.60   $176.60  
  Purchase #7 $195.28   3.383%   $201.8863   $201.89   $201.90   $201.90  
  7 purchase totals = $874.35       $930.8490   $930.86   $930.85   $931.00