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 $244.76   8.269%   $264.9992   $265.00   $265.00   $265.00  
  Purchase #2 $42.80   12.242%   $48.0396   $48.04   $48.05   $48.00  
  Purchase #3 $230.75   13.290%   $261.4167   $261.42   $261.40   $261.40  
  Purchase #4 $87.32   8.320%   $94.585   $94.59   $94.60   $94.60  
  Purchase #5 $167.27   7.274%   $179.4372   $179.44   $179.45   $179.40  
  Purchase #6 $218.44   6.709%   $233.0951   $233.10   $233.10   $233.10  
  Purchase #7 $120.98   4.486%   $126.4072   $126.41   $126.40   $126.40  
  7 purchase totals = $1,112.32       $1,207.9800   $1,208.00   $1,208.00   $1,207.90