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 $86.65   10.398%   $95.6599   $95.66   $95.65   $95.70  
  Purchase #2 $179.90   5.762%   $190.2658   $190.27   $190.25   $190.30  
  Purchase #3 $140.61   9.159%   $153.4885   $153.49   $153.50   $153.50  
  Purchase #4 $241.89   8.592%   $262.6732   $262.67   $262.65   $262.70  
  Purchase #5 $164.77   12.866%   $185.9693   $185.97   $185.95   $186.00  
  Purchase #6 $112.74   12.166%   $126.4559   $126.46   $126.45   $126.50  
  Purchase #7 $160.75   11.486%   $179.2137   $179.21   $179.20   $179.20  
  7 purchase totals = $1,087.31       $1,193.7263   $1,193.73   $1,193.65   $1,193.90