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 $24.39   6.713%   $26.0273   $26.03   $26.05   $26.00  
  Purchase #2 $192.96   7.583%   $207.5922   $207.59   $207.60   $207.60  
  Purchase #3 $144.99   13.503%   $164.568   $164.57   $164.55   $164.60  
  Purchase #4 $101.95   11.211%   $113.3796   $113.38   $113.40   $113.40  
  Purchase #5 $180.25   3.832%   $187.1572   $187.16   $187.15   $187.20  
  Purchase #6 $227.50   6.683%   $242.7038   $242.70   $242.70   $242.70  
  Purchase #7 $160.61   3.744%   $166.6232   $166.62   $166.60   $166.60  
  7 purchase totals = $1,032.65       $1,108.0513   $1,108.05   $1,108.05   $1,108.10