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 $88.95   10.113%   $97.9455   $97.95   $97.95   $97.90  
  Purchase #2 $249.79   8.356%   $270.6625   $270.66   $270.65   $270.70  
  Purchase #3 $250.45   7.301%   $268.7354   $268.74   $268.75   $268.70  
  Purchase #4 $141.62   3.756%   $146.9392   $146.94   $146.95   $146.90  
  Purchase #5 $209.57   8.214%   $226.7841   $226.78   $226.80   $226.80  
  Purchase #6 $163.80   7.480%   $176.0522   $176.05   $176.05   $176.10  
  Purchase #7 $72.86   3.453%   $75.3759   $75.38   $75.40   $75.40  
  7 purchase totals = $1,177.04       $1,262.4948   $1,262.50   $1,262.55   $1,262.50