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 $193.58   4.326%   $201.9543   $201.95   $201.95   $202.00  
  Purchase #2 $144.30   6.439%   $153.5915   $153.59   $153.60   $153.60  
  Purchase #3 $68.90   13.240%   $78.0224   $78.02   $78.00   $78.00  
  Purchase #4 $208.92   12.366%   $234.755   $234.76   $234.75   $234.80  
  Purchase #5 $235.26   7.538%   $252.9939   $252.99   $253.00   $253.00  
  Purchase #6 $229.33   13.126%   $259.4319   $259.43   $259.45   $259.40  
  Purchase #7 $163.93   9.768%   $179.9427   $179.94   $179.95   $179.90  
  7 purchase totals = $1,244.22       $1,360.6917   $1,360.68   $1,360.70   $1,360.70