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 $195.84   5.325%   $206.2685   $206.27   $206.25   $206.30  
  Purchase #2 $10.54   8.258%   $11.4104   $11.41   $11.40   $11.40  
  Purchase #3 $250.38   4.400%   $261.3967   $261.40   $261.40   $261.40  
  Purchase #4 $172.64   5.845%   $182.7308   $182.73   $182.75   $182.70  
  Purchase #5 $98.36   12.844%   $110.9934   $110.99   $111.00   $111.00  
  Purchase #6 $136.76   13.627%   $155.3963   $155.40   $155.40   $155.40  
  Purchase #7 $120.77   3.850%   $125.4196   $125.42   $125.40   $125.40  
  7 purchase totals = $985.29       $1,053.6157   $1,053.62   $1,053.60   $1,053.60