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 $166.95   5.362%   $175.9019   $175.90   $175.90   $175.90  
  Purchase #2 $10.91   4.234%   $11.3719   $11.37   $11.35   $11.40  
  Purchase #3 $114.43   4.253%   $119.2967   $119.30   $119.30   $119.30  
  Purchase #4 $76.58   12.587%   $86.2191   $86.22   $86.20   $86.20  
  Purchase #5 $169.74   7.262%   $182.0665   $182.07   $182.05   $182.10  
  Purchase #6 $104.43   9.848%   $114.7143   $114.71   $114.70   $114.70  
  Purchase #7 $72.54   4.320%   $75.6737   $75.67   $75.65   $75.70  
  7 purchase totals = $715.58       $765.2441   $765.24   $765.15   $765.30