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 $173.60   10.579%   $191.9651   $191.97   $191.95   $192.00  
  Purchase #2 $44.66   9.693%   $48.9889   $48.99   $49.00   $49.00  
  Purchase #3 $172.39   13.611%   $195.854   $195.85   $195.85   $195.90  
  Purchase #4 $238.61   5.113%   $250.8101   $250.81   $250.80   $250.80  
  Purchase #5 $249.28   10.225%   $274.7689   $274.77   $274.75   $274.80  
  Purchase #6 $175.53   10.145%   $193.3375   $193.34   $193.35   $193.30  
  Purchase #7 $199.52   4.714%   $208.9254   $208.93   $208.95   $208.90  
  7 purchase totals = $1,253.59       $1,364.6499   $1,364.66   $1,364.65   $1,364.70