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 $56.25   10.554%   $62.1866   $62.19   $62.20   $62.20  
  Purchase #2 $105.94   12.510%   $119.1931   $119.19   $119.20   $119.20  
  Purchase #3 $165.81   3.789%   $172.0925   $172.09   $172.10   $172.10  
  Purchase #4 $232.83   8.372%   $252.3225   $252.32   $252.30   $252.30  
  Purchase #5 $182.36   10.620%   $201.7266   $201.73   $201.75   $201.70  
  Purchase #6 $196.32   10.569%   $217.0691   $217.07   $217.05   $217.10  
  Purchase #7 $131.90   9.713%   $144.7114   $144.71   $144.70   $144.70  
  7 purchase totals = $1,071.41       $1,169.3018   $1,169.30   $1,169.30   $1,169.30