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 $235.68   5.250%   $248.0532   $248.05   $248.05   $248.10  
  Purchase #2 $113.88   4.715%   $119.2494   $119.25   $119.25   $119.20  
  Purchase #3 $56.95   10.275%   $62.8016   $62.80   $62.80   $62.80  
  Purchase #4 $187.77   3.110%   $193.6096   $193.61   $193.60   $193.60  
  Purchase #5 $168.93   7.439%   $181.4967   $181.50   $181.50   $181.50  
  Purchase #6 $224.36   3.874%   $233.0517   $233.05   $233.05   $233.10  
  Purchase #7 $207.73   8.271%   $224.9113   $224.91   $224.90   $224.90  
  7 purchase totals = $1,195.30       $1,263.1735   $1,263.17   $1,263.15   $1,263.20