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 $185.64   6.468%   $197.6472   $197.65   $197.65   $197.60  
  Purchase #2 $77.51   11.600%   $86.5012   $86.50   $86.50   $86.50  
  Purchase #3 $206.90   5.420%   $218.114   $218.11   $218.10   $218.10  
  Purchase #4 $89.31   12.193%   $100.1996   $100.20   $100.20   $100.20  
  Purchase #5 $233.39   12.229%   $261.9313   $261.93   $261.95   $261.90  
  Purchase #6 $199.63   6.447%   $212.5001   $212.50   $212.50   $212.50  
  Purchase #7 $192.71   13.210%   $218.167   $218.17   $218.15   $218.20  
  7 purchase totals = $1,185.09       $1,295.0604   $1,295.06   $1,295.05   $1,295.00