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 $176.45   11.594%   $196.9076   $196.91   $196.90   $196.90  
  Purchase #2 $237.84   8.685%   $258.4964   $258.50   $258.50   $258.50  
  Purchase #3 $214.46   13.212%   $242.7945   $242.79   $242.80   $242.80  
  Purchase #4 $198.86   7.716%   $214.204   $214.20   $214.20   $214.20  
  Purchase #5 $57.52   13.179%   $65.1006   $65.10   $65.10   $65.10  
  Purchase #6 $162.57   11.783%   $181.7256   $181.73   $181.75   $181.70  
  Purchase #7 $190.25   9.466%   $208.2591   $208.26   $208.25   $208.30  
  7 purchase totals = $1,237.95       $1,367.4878   $1,367.49   $1,367.50   $1,367.50