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 $56.42   9.831%   $61.9667   $61.97   $61.95   $62.00  
  Purchase #2 $241.59   7.571%   $259.8808   $259.88   $259.90   $259.90  
  Purchase #3 $11.26   10.817%   $12.478   $12.48   $12.50   $12.50  
  Purchase #4 $42.40   10.177%   $46.715   $46.72   $46.70   $46.70  
  Purchase #5 $133.64   5.628%   $141.1613   $141.16   $141.15   $141.20  
  Purchase #6 $32.26   10.615%   $35.6844   $35.68   $35.70   $35.70  
  Purchase #7 $148.74   3.509%   $153.9593   $153.96   $153.95   $154.00  
  7 purchase totals = $666.31       $711.8455   $711.85   $711.85   $712.00