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 $103.25   5.223%   $108.6427   $108.64   $108.65   $108.60  
  Purchase #2 $208.58   13.197%   $236.1063   $236.11   $236.10   $236.10  
  Purchase #3 $87.37   8.714%   $94.9834   $94.98   $95.00   $95.00  
  Purchase #4 $50.83   8.728%   $55.2664   $55.27   $55.25   $55.30  
  Purchase #5 $62.82   12.269%   $70.5274   $70.53   $70.55   $70.50  
  Purchase #6 $199.43   13.676%   $226.704   $226.70   $226.70   $226.70  
  Purchase #7 $168.88   4.679%   $176.7819   $176.78   $176.80   $176.80  
  7 purchase totals = $881.16       $969.0121   $969.01   $969.05   $969.00