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 $118.89   4.789%   $124.5836   $124.58   $124.60   $124.60  
  Purchase #2 $190.52   9.435%   $208.4956   $208.50   $208.50   $208.50  
  Purchase #3 $65.55   11.538%   $73.1132   $73.11   $73.10   $73.10  
  Purchase #4 $42.59   9.266%   $46.5364   $46.54   $46.55   $46.50  
  Purchase #5 $92.72   3.267%   $95.7492   $95.75   $95.75   $95.70  
  Purchase #6 $250.32   4.694%   $262.07   $262.07   $262.05   $262.10  
  Purchase #7 $50.40   8.154%   $54.5096   $54.51   $54.50   $54.50  
  7 purchase totals = $810.99       $865.0576   $865.06   $865.05   $865.00