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 $241.45   8.123%   $261.063   $261.06   $261.05   $261.10  
  Purchase #2 $89.94   7.247%   $96.458   $96.46   $96.45   $96.50  
  Purchase #3 $70.33   4.678%   $73.62   $73.62   $73.60   $73.60  
  Purchase #4 $35.78   8.723%   $38.9011   $38.90   $38.90   $38.90  
  Purchase #5 $145.99   12.407%   $164.103   $164.10   $164.10   $164.10  
  Purchase #6 $178.86   12.473%   $201.1692   $201.17   $201.15   $201.20  
  Purchase #7 $173.59   7.751%   $187.045   $187.05   $187.05   $187.00  
  7 purchase totals = $935.94       $1,022.3593   $1,022.36   $1,022.30   $1,022.40