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 $207.99   3.493%   $215.2551   $215.26   $215.25   $215.30  
  Purchase #2 $40.73   8.289%   $44.1061   $44.11   $44.10   $44.10  
  Purchase #3 $58.78   10.683%   $65.0595   $65.06   $65.05   $65.10  
  Purchase #4 $249.91   11.735%   $279.2369   $279.24   $279.25   $279.20  
  Purchase #5 $153.81   6.566%   $163.9092   $163.91   $163.90   $163.90  
  Purchase #6 $177.26   10.146%   $195.2448   $195.24   $195.25   $195.20  
  Purchase #7 $42.26   12.715%   $47.6334   $47.63   $47.65   $47.60  
  7 purchase totals = $930.74       $1,010.4450   $1,010.45   $1,010.45   $1,010.40