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 $242.56   8.684%   $263.6239   $263.62   $263.60   $263.60  
  Purchase #2 $91.30   12.853%   $103.0348   $103.03   $103.05   $103.00  
  Purchase #3 $228.87   5.407%   $241.245   $241.25   $241.25   $241.20  
  Purchase #4 $88.85   4.535%   $92.8793   $92.88   $92.90   $92.90  
  Purchase #5 $106.42   6.193%   $113.0106   $113.01   $113.00   $113.00  
  Purchase #6 $187.87   8.670%   $204.1583   $204.16   $204.15   $204.20  
  Purchase #7 $182.91   8.626%   $198.6878   $198.69   $198.70   $198.70  
  7 purchase totals = $1,128.78       $1,216.6397   $1,216.64   $1,216.65   $1,216.60