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 $174.67   13.758%   $198.7011   $198.70   $198.70   $198.70  
  Purchase #2 $106.85   13.564%   $121.3431   $121.34   $121.35   $121.30  
  Purchase #3 $57.68   3.508%   $59.7034   $59.70   $59.70   $59.70  
  Purchase #4 $235.91   3.326%   $243.7564   $243.76   $243.75   $243.80  
  Purchase #5 $102.55   8.730%   $111.5026   $111.50   $111.50   $111.50  
  Purchase #6 $186.56   10.794%   $206.6973   $206.70   $206.70   $206.70  
  Purchase #7 $208.42   7.595%   $224.2495   $224.25   $224.25   $224.20  
  7 purchase totals = $1,072.64       $1,165.9534   $1,165.95   $1,165.95   $1,165.90