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 $69.56   10.159%   $76.6266   $76.63   $76.65   $76.60  
  Purchase #2 $57.68   6.422%   $61.3842   $61.38   $61.40   $61.40  
  Purchase #3 $198.38   3.810%   $205.9383   $205.94   $205.95   $205.90  
  Purchase #4 $235.81   6.459%   $251.041   $251.04   $251.05   $251.00  
  Purchase #5 $183.64   13.248%   $207.9686   $207.97   $207.95   $208.00  
  Purchase #6 $41.58   4.324%   $43.3779   $43.38   $43.40   $43.40  
  Purchase #7 $102.81   6.186%   $109.1698   $109.17   $109.15   $109.20  
  7 purchase totals = $889.46       $955.5064   $955.51   $955.55   $955.50