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 $204.78   5.354%   $215.7439   $215.74   $215.75   $215.70  
  Purchase #2 $10.53   9.158%   $11.4943   $11.49   $11.50   $11.50  
  Purchase #3 $46.81   3.542%   $48.468   $48.47   $48.45   $48.50  
  Purchase #4 $185.83   7.784%   $200.295   $200.30   $200.30   $200.30  
  Purchase #5 $69.34   7.633%   $74.6327   $74.63   $74.65   $74.60  
  Purchase #6 $193.43   3.859%   $200.8945   $200.89   $200.90   $200.90  
  Purchase #7 $15.60   13.160%   $17.653   $17.65   $17.65   $17.70  
  7 purchase totals = $726.32       $769.1814   $769.17   $769.20   $769.20