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 $241.27   8.777%   $262.4463   $262.45   $262.45   $262.40  
  Purchase #2 $54.91   13.245%   $62.1828   $62.18   $62.20   $62.20  
  Purchase #3 $13.91   3.604%   $14.4113   $14.41   $14.40   $14.40  
  Purchase #4 $198.90   13.593%   $225.9365   $225.94   $225.95   $225.90  
  Purchase #5 $26.72   13.834%   $30.4164   $30.42   $30.40   $30.40  
  Purchase #6 $103.76   9.113%   $113.2156   $113.22   $113.20   $113.20  
  Purchase #7 $226.32   6.488%   $241.0036   $241.00   $241.00   $241.00  
  7 purchase totals = $865.79       $949.6125   $949.62   $949.60   $949.50