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 $248.96   7.625%   $267.9432   $267.94   $267.95   $267.90  
  Purchase #2 $241.75   8.680%   $262.7339   $262.73   $262.75   $262.70  
  Purchase #3 $97.86   10.271%   $107.9112   $107.91   $107.90   $107.90  
  Purchase #4 $196.29   4.431%   $204.9876   $204.99   $205.00   $205.00  
  Purchase #5 $83.63   4.478%   $87.375   $87.38   $87.40   $87.40  
  Purchase #6 $112.91   12.272%   $126.7663   $126.77   $126.75   $126.80  
  Purchase #7 $140.76   9.824%   $154.5883   $154.59   $154.60   $154.60  
  7 purchase totals = $1,122.16       $1,212.3055   $1,212.31   $1,212.35   $1,212.30