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 $206.81   4.293%   $215.6884   $215.69   $215.70   $215.70  
  Purchase #2 $101.69   12.118%   $114.0128   $114.01   $114.00   $114.00  
  Purchase #3 $36.93   8.554%   $40.089   $40.09   $40.10   $40.10  
  Purchase #4 $169.85   4.231%   $177.0364   $177.04   $177.05   $177.00  
  Purchase #5 $233.59   13.507%   $265.141   $265.14   $265.15   $265.10  
  Purchase #6 $114.31   3.129%   $117.8868   $117.89   $117.90   $117.90  
  Purchase #7 $186.94   5.350%   $196.9413   $196.94   $196.95   $196.90  
  7 purchase totals = $1,050.12       $1,126.7957   $1,126.80   $1,126.85   $1,126.70