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 $86.30   11.752%   $96.442   $96.44   $96.45   $96.40  
  Purchase #2 $232.71   7.357%   $249.8305   $249.83   $249.85   $249.80  
  Purchase #3 $83.94   3.551%   $86.9207   $86.92   $86.90   $86.90  
  Purchase #4 $56.99   8.588%   $61.8843   $61.88   $61.90   $61.90  
  Purchase #5 $165.79   5.745%   $175.3146   $175.31   $175.30   $175.30  
  Purchase #6 $91.74   13.332%   $103.9708   $103.97   $103.95   $104.00  
  Purchase #7 $164.75   12.520%   $185.3767   $185.38   $185.40   $185.40  
  7 purchase totals = $882.22       $959.7396   $959.73   $959.75   $959.70