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 $184.48   9.827%   $202.6088   $202.61   $202.60   $202.60  
  Purchase #2 $24.63   6.244%   $26.1679   $26.17   $26.15   $26.20  
  Purchase #3 $208.95   7.419%   $224.452   $224.45   $224.45   $224.50  
  Purchase #4 $237.70   13.135%   $268.9219   $268.92   $268.90   $268.90  
  Purchase #5 $119.66   4.458%   $124.9944   $124.99   $125.00   $125.00  
  Purchase #6 $202.90   11.209%   $225.6431   $225.64   $225.65   $225.60  
  Purchase #7 $248.34   9.382%   $271.6393   $271.64   $271.65   $271.60  
  7 purchase totals = $1,226.66       $1,344.4274   $1,344.42   $1,344.40   $1,344.40