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 $235.67   9.309%   $257.6085   $257.61   $257.60   $257.60  
  Purchase #2 $197.52   5.387%   $208.1604   $208.16   $208.15   $208.20  
  Purchase #3 $237.29   7.238%   $254.4651   $254.47   $254.45   $254.50  
  Purchase #4 $221.78   7.143%   $237.6217   $237.62   $237.60   $237.60  
  Purchase #5 $226.45   6.657%   $241.5248   $241.52   $241.50   $241.50  
  Purchase #6 $104.50   9.119%   $114.0294   $114.03   $114.05   $114.00  
  Purchase #7 $48.88   5.633%   $51.6334   $51.63   $51.65   $51.60  
  7 purchase totals = $1,272.09       $1,365.0433   $1,365.04   $1,365.00   $1,365.00