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 $201.39   3.544%   $208.5273   $208.53   $208.55   $208.50  
  Purchase #2 $211.74   10.863%   $234.7413   $234.74   $234.75   $234.70  
  Purchase #3 $42.62   7.212%   $45.6938   $45.69   $45.70   $45.70  
  Purchase #4 $58.49   10.729%   $64.7654   $64.77   $64.75   $64.80  
  Purchase #5 $236.43   7.362%   $253.836   $253.84   $253.85   $253.80  
  Purchase #6 $83.32   3.190%   $85.9779   $85.98   $86.00   $86.00  
  Purchase #7 $227.72   12.418%   $255.9983   $256.00   $256.00   $256.00  
  7 purchase totals = $1,061.71       $1,149.5400   $1,149.55   $1,149.60   $1,149.50