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 $182.96   5.264%   $192.591   $192.59   $192.60   $192.60  
  Purchase #2 $167.76   5.449%   $176.9012   $176.90   $176.90   $176.90  
  Purchase #3 $180.71   9.532%   $197.9353   $197.94   $197.95   $197.90  
  Purchase #4 $7.99   3.626%   $8.2797   $8.28   $8.30   $8.30  
  Purchase #5 $84.41   11.159%   $93.8293   $93.83   $93.85   $93.80  
  Purchase #6 $155.31   10.418%   $171.4902   $171.49   $171.50   $171.50  
  Purchase #7 $7.70   5.662%   $8.136   $8.14   $8.15   $8.10  
  7 purchase totals = $786.84       $849.1627   $849.17   $849.25   $849.10