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 $41.64   5.588%   $43.9668   $43.97   $43.95   $44.00  
  Purchase #2 $119.43   12.472%   $134.3253   $134.33   $134.35   $134.30  
  Purchase #3 $34.80   5.406%   $36.6813   $36.68   $36.70   $36.70  
  Purchase #4 $114.75   3.608%   $118.8902   $118.89   $118.90   $118.90  
  Purchase #5 $112.99   8.590%   $122.6958   $122.70   $122.70   $122.70  
  Purchase #6 $190.57   5.208%   $200.4949   $200.49   $200.50   $200.50  
  Purchase #7 $74.45   5.646%   $78.6534   $78.65   $78.65   $78.70  
  7 purchase totals = $688.63       $735.7077   $735.71   $735.75   $735.80