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 $182.61   5.693%   $193.006   $193.01   $193.00   $193.00  
  Purchase #2 $113.54   11.599%   $126.7095   $126.71   $126.70   $126.70  
  Purchase #3 $49.35   11.639%   $55.0938   $55.09   $55.10   $55.10  
  Purchase #4 $243.32   12.804%   $274.4747   $274.47   $274.45   $274.50  
  Purchase #5 $116.47   6.122%   $123.6003   $123.60   $123.60   $123.60  
  Purchase #6 $58.43   8.551%   $63.4263   $63.43   $63.45   $63.40  
  Purchase #7 $141.45   3.602%   $146.545   $146.55   $146.55   $146.50  
  7 purchase totals = $905.17       $982.8556   $982.86   $982.85   $982.80