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 $61.68   3.261%   $63.6914   $63.69   $63.70   $63.70  
  Purchase #2 $154.82   4.808%   $162.2637   $162.26   $162.25   $162.30  
  Purchase #3 $244.39   12.783%   $275.6304   $275.63   $275.65   $275.60  
  Purchase #4 $167.73   8.540%   $182.0541   $182.05   $182.05   $182.10  
  Purchase #5 $145.56   13.390%   $165.0505   $165.05   $165.05   $165.10  
  Purchase #6 $190.49   4.561%   $199.1782   $199.18   $199.20   $199.20  
  Purchase #7 $222.71   11.827%   $249.0499   $249.05   $249.05   $249.00  
  7 purchase totals = $1,187.38       $1,296.9182   $1,296.91   $1,296.95   $1,297.00