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 $67.33   13.422%   $76.367   $76.37   $76.35   $76.40  
  Purchase #2 $166.59   9.571%   $182.5343   $182.53   $182.55   $182.50  
  Purchase #3 $146.93   12.285%   $164.9804   $164.98   $165.00   $165.00  
  Purchase #4 $181.49   5.119%   $190.7805   $190.78   $190.80   $190.80  
  Purchase #5 $132.83   6.432%   $141.3736   $141.37   $141.35   $141.40  
  Purchase #6 $171.59   11.195%   $190.7995   $190.80   $190.80   $190.80  
  Purchase #7 $32.26   13.706%   $36.6816   $36.68   $36.70   $36.70  
  7 purchase totals = $899.02       $983.5169   $983.51   $983.55   $983.60