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 $173.32   3.422%   $179.251   $179.25   $179.25   $179.30  
  Purchase #2 $195.64   3.619%   $202.7202   $202.72   $202.70   $202.70  
  Purchase #3 $207.54   13.273%   $235.0868   $235.09   $235.10   $235.10  
  Purchase #4 $86.44   13.627%   $98.2192   $98.22   $98.20   $98.20  
  Purchase #5 $68.60   6.182%   $72.8409   $72.84   $72.85   $72.80  
  Purchase #6 $148.60   6.248%   $157.8845   $157.88   $157.90   $157.90  
  Purchase #7 $76.46   13.716%   $86.9473   $86.95   $86.95   $86.90  
  7 purchase totals = $956.60       $1,032.9499   $1,032.95   $1,032.95   $1,032.90