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 $214.73   10.258%   $236.757   $236.76   $236.75   $236.80  
  Purchase #2 $145.81   9.150%   $159.1516   $159.15   $159.15   $159.20  
  Purchase #3 $93.95   8.146%   $101.6032   $101.60   $101.60   $101.60  
  Purchase #4 $193.77   5.636%   $204.6909   $204.69   $204.70   $204.70  
  Purchase #5 $15.26   12.868%   $17.2237   $17.22   $17.20   $17.20  
  Purchase #6 $147.77   9.285%   $161.4904   $161.49   $161.50   $161.50  
  Purchase #7 $38.68   13.274%   $43.8144   $43.81   $43.80   $43.80  
  7 purchase totals = $849.97       $924.7312   $924.72   $924.70   $924.80