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 $182.26   10.252%   $200.9453   $200.95   $200.95   $200.90  
  Purchase #2 $44.75   4.192%   $46.6259   $46.63   $46.65   $46.60  
  Purchase #3 $130.29   9.185%   $142.2571   $142.26   $142.25   $142.30  
  Purchase #4 $175.27   13.483%   $198.9017   $198.90   $198.90   $198.90  
  Purchase #5 $178.87   4.219%   $186.4165   $186.42   $186.40   $186.40  
  Purchase #6 $28.70   4.505%   $29.9929   $29.99   $30.00   $30.00  
  Purchase #7 $38.72   13.480%   $43.9395   $43.94   $43.95   $43.90  
  7 purchase totals = $778.86       $849.0789   $849.09   $849.10   $849.00