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 $62.87   8.574%   $68.2605   $68.26   $68.25   $68.30  
  Purchase #2 $115.72   6.336%   $123.052   $123.05   $123.05   $123.10  
  Purchase #3 $169.77   12.232%   $190.5363   $190.54   $190.55   $190.50  
  Purchase #4 $23.99   9.295%   $26.2199   $26.22   $26.20   $26.20  
  Purchase #5 $177.40   9.128%   $193.5931   $193.59   $193.60   $193.60  
  Purchase #6 $249.61   12.682%   $281.2655   $281.27   $281.25   $281.30  
  Purchase #7 $183.73   3.754%   $190.6272   $190.63   $190.65   $190.60  
  7 purchase totals = $983.09       $1,073.5545   $1,073.56   $1,073.55   $1,073.60