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 $208.31   7.615%   $224.1728   $224.17   $224.15   $224.20  
  Purchase #2 $235.49   4.634%   $246.4026   $246.40   $246.40   $246.40  
  Purchase #3 $62.60   6.854%   $66.8906   $66.89   $66.90   $66.90  
  Purchase #4 $84.64   3.525%   $87.6236   $87.62   $87.60   $87.60  
  Purchase #5 $98.89   6.734%   $105.5493   $105.55   $105.55   $105.50  
  Purchase #6 $239.50   9.767%   $262.892   $262.89   $262.90   $262.90  
  Purchase #7 $28.63   9.162%   $31.2531   $31.25   $31.25   $31.30  
  7 purchase totals = $958.06       $1,024.7840   $1,024.77   $1,024.75   $1,024.80