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 $57.68   8.434%   $62.5447   $62.54   $62.55   $62.50  
  Purchase #2 $201.67   8.861%   $219.54   $219.54   $219.55   $219.50  
  Purchase #3 $162.31   12.355%   $182.3634   $182.36   $182.35   $182.40  
  Purchase #4 $133.75   11.853%   $149.6034   $149.60   $149.60   $149.60  
  Purchase #5 $203.32   9.254%   $222.1352   $222.14   $222.15   $222.10  
  Purchase #6 $200.83   3.414%   $207.6863   $207.69   $207.70   $207.70  
  Purchase #7 $240.65   8.793%   $261.8104   $261.81   $261.80   $261.80  
  7 purchase totals = $1,200.21       $1,305.6834   $1,305.68   $1,305.70   $1,305.60