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 $58.25   6.390%   $61.9722   $61.97   $61.95   $62.00  
  Purchase #2 $19.92   11.531%   $22.217   $22.22   $22.20   $22.20  
  Purchase #3 $186.76   10.296%   $205.9888   $205.99   $206.00   $206.00  
  Purchase #4 $63.76   11.380%   $71.0159   $71.02   $71.00   $71.00  
  Purchase #5 $129.51   3.537%   $134.0908   $134.09   $134.10   $134.10  
  Purchase #6 $83.32   4.149%   $86.7769   $86.78   $86.80   $86.80  
  Purchase #7 $196.93   8.765%   $214.1909   $214.19   $214.20   $214.20  
  7 purchase totals = $738.45       $796.2525   $796.26   $796.25   $796.30