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 $68.36   11.803%   $76.4285   $76.43   $76.45   $76.40  
  Purchase #2 $167.87   4.642%   $175.6625   $175.66   $175.65   $175.70  
  Purchase #3 $30.83   4.319%   $32.1615   $32.16   $32.15   $32.20  
  Purchase #4 $47.80   12.794%   $53.9155   $53.92   $53.90   $53.90  
  Purchase #5 $133.76   4.416%   $139.6668   $139.67   $139.65   $139.70  
  Purchase #6 $32.77   6.644%   $34.9472   $34.95   $34.95   $34.90  
  Purchase #7 $32.75   7.548%   $35.222   $35.22   $35.20   $35.20  
  7 purchase totals = $514.14       $548.0040   $548.01   $547.95   $548.00