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 $167.96   8.768%   $182.6867   $182.69   $182.70   $182.70  
  Purchase #2 $176.83   11.859%   $197.8003   $197.80   $197.80   $197.80  
  Purchase #3 $106.84   3.226%   $110.2867   $110.29   $110.30   $110.30  
  Purchase #4 $55.95   7.109%   $59.9275   $59.93   $59.95   $59.90  
  Purchase #5 $188.69   8.511%   $204.7494   $204.75   $204.75   $204.70  
  Purchase #6 $77.49   3.724%   $80.3757   $80.38   $80.40   $80.40  
  Purchase #7 $164.32   13.686%   $186.8088   $186.81   $186.80   $186.80  
  7 purchase totals = $938.08       $1,022.6351   $1,022.65   $1,022.70   $1,022.60