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 $244.51   8.679%   $265.731   $265.73   $265.75   $265.70  
  Purchase #2 $182.88   7.167%   $195.987   $195.99   $196.00   $196.00  
  Purchase #3 $95.83   9.482%   $104.9166   $104.92   $104.90   $104.90  
  Purchase #4 $12.25   3.296%   $12.6538   $12.65   $12.65   $12.70  
  Purchase #5 $242.36   3.487%   $250.8111   $250.81   $250.80   $250.80  
  Purchase #6 $90.54   12.397%   $101.7642   $101.76   $101.75   $101.80  
  Purchase #7 $138.34   12.353%   $155.4291   $155.43   $155.45   $155.40  
  7 purchase totals = $1,006.71       $1,087.2928   $1,087.29   $1,087.30   $1,087.30