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 $186.71   7.452%   $200.6236   $200.62   $200.60   $200.60  
  Purchase #2 $63.78   9.119%   $69.5961   $69.60   $69.60   $69.60  
  Purchase #3 $247.41   12.206%   $277.6089   $277.61   $277.60   $277.60  
  Purchase #4 $185.32   12.357%   $208.22   $208.22   $208.20   $208.20  
  Purchase #5 $46.78   10.680%   $51.7761   $51.78   $51.80   $51.80  
  Purchase #6 $242.52   11.612%   $270.6814   $270.68   $270.70   $270.70  
  Purchase #7 $55.64   13.794%   $63.315   $63.32   $63.30   $63.30  
  7 purchase totals = $1,028.16       $1,141.8211   $1,141.83   $1,141.80   $1,141.80