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 $86.53   13.538%   $98.2444   $98.24   $98.25   $98.20  
  Purchase #2 $243.28   12.626%   $273.9965   $274.00   $274.00   $274.00  
  Purchase #3 $81.45   12.609%   $91.72   $91.72   $91.70   $91.70  
  Purchase #4 $236.96   8.662%   $257.4855   $257.49   $257.50   $257.50  
  Purchase #5 $163.34   4.419%   $170.558   $170.56   $170.55   $170.60  
  Purchase #6 $23.37   4.583%   $24.441   $24.44   $24.45   $24.40  
  Purchase #7 $32.59   3.161%   $33.6202   $33.62   $33.60   $33.60  
  7 purchase totals = $867.52       $950.0656   $950.07   $950.05   $950.00