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 $141.63   8.723%   $153.9844   $153.98   $154.00   $154.00  
  Purchase #2 $85.67   11.659%   $95.6583   $95.66   $95.65   $95.70  
  Purchase #3 $234.86   5.704%   $248.2564   $248.26   $248.25   $248.30  
  Purchase #4 $200.40   4.113%   $208.6425   $208.64   $208.65   $208.60  
  Purchase #5 $240.53   7.202%   $257.853   $257.85   $257.85   $257.90  
  Purchase #6 $237.57   8.596%   $257.9915   $257.99   $258.00   $258.00  
  Purchase #7 $213.74   12.228%   $239.8761   $239.88   $239.90   $239.90  
  7 purchase totals = $1,354.40       $1,462.2622   $1,462.26   $1,462.30   $1,462.40