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 $72.49   5.354%   $76.3711   $76.37   $76.35   $76.40  
  Purchase #2 $13.97   4.262%   $14.5654   $14.57   $14.55   $14.60  
  Purchase #3 $164.31   7.555%   $176.7236   $176.72   $176.70   $176.70  
  Purchase #4 $82.66   3.195%   $85.301   $85.30   $85.30   $85.30  
  Purchase #5 $240.63   10.379%   $265.605   $265.61   $265.60   $265.60  
  Purchase #6 $39.26   6.109%   $41.6584   $41.66   $41.65   $41.70  
  Purchase #7 $237.76   11.807%   $265.8323   $265.83   $265.85   $265.80  
  7 purchase totals = $851.08       $926.0568   $926.06   $926.00   $926.10