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 $24.97   4.692%   $26.1416   $26.14   $26.15   $26.10  
  Purchase #2 $117.94   11.825%   $131.8864   $131.89   $131.90   $131.90  
  Purchase #3 $6.40   5.725%   $6.7664   $6.77   $6.75   $6.80  
  Purchase #4 $249.26   5.477%   $262.912   $262.91   $262.90   $262.90  
  Purchase #5 $133.62   12.282%   $150.0312   $150.03   $150.05   $150.00  
  Purchase #6 $146.75   8.440%   $159.1357   $159.14   $159.15   $159.10  
  Purchase #7 $188.26   13.271%   $213.244   $213.24   $213.25   $213.20  
  7 purchase totals = $867.20       $950.1173   $950.12   $950.15   $950.00