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 $207.85   7.772%   $224.0041   $224.00   $224.00   $224.00  
  Purchase #2 $68.90   7.334%   $73.9531   $73.95   $73.95   $74.00  
  Purchase #3 $244.26   13.839%   $278.0631   $278.06   $278.05   $278.10  
  Purchase #4 $71.51   3.828%   $74.2474   $74.25   $74.25   $74.20  
  Purchase #5 $190.86   8.216%   $206.5411   $206.54   $206.55   $206.50  
  Purchase #6 $51.56   12.287%   $57.8952   $57.90   $57.90   $57.90  
  Purchase #7 $184.55   12.795%   $208.1632   $208.16   $208.15   $208.20  
  7 purchase totals = $1,019.49       $1,122.8672   $1,122.86   $1,122.85   $1,122.90