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 $67.26   8.484%   $72.9663   $72.97   $72.95   $73.00  
  Purchase #2 $184.59   6.193%   $196.0217   $196.02   $196.00   $196.00  
  Purchase #3 $71.95   6.177%   $76.3944   $76.39   $76.40   $76.40  
  Purchase #4 $158.56   4.185%   $165.1957   $165.20   $165.20   $165.20  
  Purchase #5 $141.82   11.197%   $157.6996   $157.70   $157.70   $157.70  
  Purchase #6 $248.92   11.623%   $277.852   $277.85   $277.85   $277.90  
  Purchase #7 $213.46   13.401%   $242.0658   $242.07   $242.05   $242.10  
  7 purchase totals = $1,086.56       $1,188.1955   $1,188.20   $1,188.15   $1,188.30