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 $81.26   5.637%   $85.8406   $85.84   $85.85   $85.80  
  Purchase #2 $6.38   9.618%   $6.9936   $6.99   $7.00   $7.00  
  Purchase #3 $92.26   6.207%   $97.9866   $97.99   $98.00   $98.00  
  Purchase #4 $179.84   3.585%   $186.2873   $186.29   $186.30   $186.30  
  Purchase #5 $222.31   10.511%   $245.677   $245.68   $245.70   $245.70  
  Purchase #6 $112.34   10.789%   $124.4604   $124.46   $124.45   $124.50  
  Purchase #7 $190.54   9.206%   $208.0811   $208.08   $208.10   $208.10  
  7 purchase totals = $884.93       $955.3266   $955.33   $955.40   $955.40