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 $202.41   5.602%   $213.749   $213.75   $213.75   $213.70  
  Purchase #2 $77.83   10.254%   $85.8107   $85.81   $85.80   $85.80  
  Purchase #3 $26.94   4.262%   $28.0882   $28.09   $28.10   $28.10  
  Purchase #4 $94.98   4.134%   $98.9065   $98.91   $98.90   $98.90  
  Purchase #5 $30.97   5.747%   $32.7498   $32.75   $32.75   $32.70  
  Purchase #6 $51.92   7.843%   $55.9921   $55.99   $56.00   $56.00  
  Purchase #7 $205.25   5.786%   $217.1258   $217.13   $217.15   $217.10  
  7 purchase totals = $690.30       $732.4221   $732.43   $732.45   $732.30