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 $95.43   5.787%   $100.9525   $100.95   $100.95   $101.00  
  Purchase #2 $29.32   13.250%   $33.2049   $33.20   $33.20   $33.20  
  Purchase #3 $87.63   6.285%   $93.1375   $93.14   $93.15   $93.10  
  Purchase #4 $42.60   5.795%   $45.0687   $45.07   $45.05   $45.10  
  Purchase #5 $73.72   4.409%   $76.9703   $76.97   $76.95   $77.00  
  Purchase #6 $174.72   7.699%   $188.1717   $188.17   $188.15   $188.20  
  Purchase #7 $233.62   5.508%   $246.4878   $246.49   $246.50   $246.50  
  7 purchase totals = $737.04       $783.9934   $783.99   $783.95   $784.10