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 $71.63   7.329%   $76.8798   $76.88   $76.90   $76.90  
  Purchase #2 $156.43   4.387%   $163.2926   $163.29   $163.30   $163.30  
  Purchase #3 $240.45   5.820%   $254.4442   $254.44   $254.45   $254.40  
  Purchase #4 $7.58   8.625%   $8.2338   $8.23   $8.25   $8.20  
  Purchase #5 $186.63   6.453%   $198.6732   $198.67   $198.65   $198.70  
  Purchase #6 $10.69   5.426%   $11.27   $11.27   $11.25   $11.30  
  Purchase #7 $11.88   11.264%   $13.2182   $13.22   $13.20   $13.20  
  7 purchase totals = $685.29       $726.0118   $726.00   $726.00   $726.00