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 $58.95   11.694%   $65.8436   $65.84   $65.85   $65.80  
  Purchase #2 $67.27   13.389%   $76.2768   $76.28   $76.30   $76.30  
  Purchase #3 $62.60   5.176%   $65.8402   $65.84   $65.85   $65.80  
  Purchase #4 $177.71   5.655%   $187.7595   $187.76   $187.75   $187.80  
  Purchase #5 $195.42   3.321%   $201.9099   $201.91   $201.90   $201.90  
  Purchase #6 $248.32   6.567%   $264.6272   $264.63   $264.65   $264.60  
  Purchase #7 $233.27   6.579%   $248.6168   $248.62   $248.60   $248.60  
  7 purchase totals = $1,043.54       $1,110.8740   $1,110.88   $1,110.90   $1,110.80