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 $214.72   11.379%   $239.153   $239.15   $239.15   $239.20  
  Purchase #2 $66.57   4.793%   $69.7607   $69.76   $69.75   $69.80  
  Purchase #3 $176.79   8.651%   $192.0841   $192.08   $192.10   $192.10  
  Purchase #4 $162.96   5.510%   $171.9391   $171.94   $171.95   $171.90  
  Purchase #5 $134.68   5.429%   $141.9918   $141.99   $142.00   $142.00  
  Purchase #6 $213.73   13.311%   $242.1796   $242.18   $242.20   $242.20  
  Purchase #7 $161.46   4.322%   $168.4383   $168.44   $168.45   $168.40  
  7 purchase totals = $1,130.91       $1,225.5466   $1,225.54   $1,225.60   $1,225.60