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 $248.77   5.327%   $262.022   $262.02   $262.00   $262.00  
  Purchase #2 $55.75   6.266%   $59.2433   $59.24   $59.25   $59.20  
  Purchase #3 $206.69   12.692%   $232.9231   $232.92   $232.90   $232.90  
  Purchase #4 $93.43   12.319%   $104.9396   $104.94   $104.95   $104.90  
  Purchase #5 $10.29   9.441%   $11.2615   $11.26   $11.25   $11.30  
  Purchase #6 $46.83   12.280%   $52.5807   $52.58   $52.60   $52.60  
  Purchase #7 $25.80   3.474%   $26.6963   $26.70   $26.70   $26.70  
  7 purchase totals = $687.56       $749.6665   $749.66   $749.65   $749.60