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 $162.93   11.856%   $182.247   $182.25   $182.25   $182.20  
  Purchase #2 $224.89   11.453%   $250.6467   $250.65   $250.65   $250.60  
  Purchase #3 $57.83   3.298%   $59.7372   $59.74   $59.75   $59.70  
  Purchase #4 $56.31   8.624%   $61.1662   $61.17   $61.15   $61.20  
  Purchase #5 $171.45   13.190%   $194.0643   $194.06   $194.05   $194.10  
  Purchase #6 $140.71   11.786%   $157.2941   $157.29   $157.30   $157.30  
  Purchase #7 $208.47   10.801%   $230.9868   $230.99   $231.00   $231.00  
  7 purchase totals = $1,022.59       $1,136.1423   $1,136.15   $1,136.15   $1,136.10