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 $196.26   9.560%   $215.0225   $215.02   $215.00   $215.00  
  Purchase #2 $131.65   3.838%   $136.7027   $136.70   $136.70   $136.70  
  Purchase #3 $12.50   12.593%   $14.0741   $14.07   $14.05   $14.10  
  Purchase #4 $217.38   9.711%   $238.4898   $238.49   $238.50   $238.50  
  Purchase #5 $207.36   6.597%   $221.0395   $221.04   $221.05   $221.00  
  Purchase #6 $71.50   9.253%   $78.1159   $78.12   $78.10   $78.10  
  Purchase #7 $193.30   5.671%   $204.262   $204.26   $204.25   $204.30  
  7 purchase totals = $1,029.95       $1,107.7065   $1,107.70   $1,107.65   $1,107.70