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 $41.67   3.327%   $43.0564   $43.06   $43.05   $43.10  
  Purchase #2 $154.63   9.338%   $169.0693   $169.07   $169.05   $169.10  
  Purchase #3 $201.76   3.175%   $208.1659   $208.17   $208.15   $208.20  
  Purchase #4 $194.35   9.106%   $212.0475   $212.05   $212.05   $212.00  
  Purchase #5 $9.78   6.149%   $10.3814   $10.38   $10.40   $10.40  
  Purchase #6 $103.96   9.862%   $114.2125   $114.21   $114.20   $114.20  
  Purchase #7 $151.54   11.230%   $168.5579   $168.56   $168.55   $168.60  
  7 purchase totals = $857.69       $925.4909   $925.50   $925.45   $925.60