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 $61.36   13.478%   $69.6301   $69.63   $69.65   $69.60  
  Purchase #2 $226.67   5.139%   $238.3186   $238.32   $238.30   $238.30  
  Purchase #3 $149.91   3.144%   $154.6232   $154.62   $154.60   $154.60  
  Purchase #4 $38.62   4.263%   $40.2664   $40.27   $40.25   $40.30  
  Purchase #5 $206.99   10.775%   $229.2932   $229.29   $229.30   $229.30  
  Purchase #6 $56.88   4.438%   $59.4043   $59.40   $59.40   $59.40  
  Purchase #7 $168.27   7.284%   $180.5268   $180.53   $180.55   $180.50  
  7 purchase totals = $908.70       $972.0626   $972.06   $972.05   $972.00