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 $22.86   7.316%   $24.5324   $24.53   $24.55   $24.50  
  Purchase #2 $168.58   3.576%   $174.6084   $174.61   $174.60   $174.60  
  Purchase #3 $246.51   5.416%   $259.861   $259.86   $259.85   $259.90  
  Purchase #4 $182.58   5.708%   $193.0017   $193.00   $193.00   $193.00  
  Purchase #5 $218.48   4.823%   $229.0173   $229.02   $229.00   $229.00  
  Purchase #6 $143.81   5.868%   $152.2488   $152.25   $152.25   $152.20  
  Purchase #7 $201.71   4.479%   $210.7446   $210.74   $210.75   $210.70  
  7 purchase totals = $1,184.53       $1,244.0142   $1,244.01   $1,244.00   $1,243.90