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 $115.94   6.324%   $123.272   $123.27   $123.25   $123.30  
  Purchase #2 $73.68   4.451%   $76.9595   $76.96   $76.95   $77.00  
  Purchase #3 $81.67   5.828%   $86.4297   $86.43   $86.45   $86.40  
  Purchase #4 $171.32   9.589%   $187.7479   $187.75   $187.75   $187.70  
  Purchase #5 $130.36   8.296%   $141.1747   $141.17   $141.15   $141.20  
  Purchase #6 $89.80   4.199%   $93.5707   $93.57   $93.55   $93.60  
  Purchase #7 $23.95   11.716%   $26.756   $26.76   $26.75   $26.80  
  7 purchase totals = $686.72       $735.9105   $735.91   $735.85   $736.00