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 $59.49   6.728%   $63.4925   $63.49   $63.50   $63.50  
  Purchase #2 $74.28   9.253%   $81.1531   $81.15   $81.15   $81.20  
  Purchase #3 $211.81   7.691%   $228.1003   $228.10   $228.10   $228.10  
  Purchase #4 $134.71   8.739%   $146.4823   $146.48   $146.50   $146.50  
  Purchase #5 $156.76   11.340%   $174.5366   $174.54   $174.55   $174.50  
  Purchase #6 $178.72   7.422%   $191.9846   $191.98   $192.00   $192.00  
  Purchase #7 $203.78   11.329%   $226.8662   $226.87   $226.85   $226.90  
  7 purchase totals = $1,019.55       $1,112.6156   $1,112.61   $1,112.65   $1,112.70