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 $102.92   10.855%   $114.092   $114.09   $114.10   $114.10  
  Purchase #2 $86.77   10.116%   $95.5477   $95.55   $95.55   $95.50  
  Purchase #3 $70.85   8.809%   $77.0912   $77.09   $77.10   $77.10  
  Purchase #4 $246.49   5.184%   $259.268   $259.27   $259.25   $259.30  
  Purchase #5 $169.67   10.843%   $188.0673   $188.07   $188.05   $188.10  
  Purchase #6 $183.67   13.688%   $208.8107   $208.81   $208.80   $208.80  
  Purchase #7 $164.84   4.449%   $172.1737   $172.17   $172.15   $172.20  
  7 purchase totals = $1,025.21       $1,115.0506   $1,115.05   $1,115.00   $1,115.10