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 $196.91   8.795%   $214.2282   $214.23   $214.25   $214.20  
  Purchase #2 $98.69   13.463%   $111.9766   $111.98   $112.00   $112.00  
  Purchase #3 $24.66   6.734%   $26.3206   $26.32   $26.30   $26.30  
  Purchase #4 $52.32   11.844%   $58.5168   $58.52   $58.50   $58.50  
  Purchase #5 $95.27   4.545%   $99.6   $99.60   $99.60   $99.60  
  Purchase #6 $70.38   12.339%   $79.0642   $79.06   $79.05   $79.10  
  Purchase #7 $177.31   5.130%   $186.406   $186.41   $186.40   $186.40  
  7 purchase totals = $715.54       $776.1124   $776.12   $776.10   $776.10