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 $62.45   10.439%   $68.9692   $68.97   $68.95   $69.00  
  Purchase #2 $162.69   12.627%   $183.2329   $183.23   $183.25   $183.20  
  Purchase #3 $111.76   11.222%   $124.3017   $124.30   $124.30   $124.30  
  Purchase #4 $108.97   3.851%   $113.1664   $113.17   $113.15   $113.20  
  Purchase #5 $235.47   11.463%   $262.4619   $262.46   $262.45   $262.50  
  Purchase #6 $119.78   12.552%   $134.8148   $134.81   $134.80   $134.80  
  Purchase #7 $145.28   8.555%   $157.7087   $157.71   $157.70   $157.70  
  7 purchase totals = $946.40       $1,044.6556   $1,044.65   $1,044.60   $1,044.70