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 $112.26   12.386%   $126.1645   $126.16   $126.15   $126.20  
  Purchase #2 $171.38   13.312%   $194.1941   $194.19   $194.20   $194.20  
  Purchase #3 $43.34   9.534%   $47.472   $47.47   $47.45   $47.50  
  Purchase #4 $107.85   8.725%   $117.2599   $117.26   $117.25   $117.30  
  Purchase #5 $185.90   10.420%   $205.2708   $205.27   $205.25   $205.30  
  Purchase #6 $224.88   10.587%   $248.688   $248.69   $248.70   $248.70  
  Purchase #7 $91.77   6.454%   $97.6928   $97.69   $97.70   $97.70  
  7 purchase totals = $937.38       $1,036.7421   $1,036.73   $1,036.70   $1,036.90