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 $228.69   3.144%   $235.88   $235.88   $235.90   $235.90  
  Purchase #2 $50.76   4.872%   $53.233   $53.23   $53.25   $53.20  
  Purchase #3 $121.83   4.752%   $127.6194   $127.62   $127.60   $127.60  
  Purchase #4 $8.54   9.226%   $9.3279   $9.33   $9.35   $9.30  
  Purchase #5 $185.75   4.149%   $193.4568   $193.46   $193.45   $193.50  
  Purchase #6 $201.81   6.375%   $214.6754   $214.68   $214.70   $214.70  
  Purchase #7 $55.61   8.322%   $60.2379   $60.24   $60.25   $60.20  
  7 purchase totals = $852.99       $894.4304   $894.44   $894.50   $894.40