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 $232.99   5.235%   $245.187   $245.19   $245.20   $245.20  
  Purchase #2 $216.38   7.683%   $233.0045   $233.00   $233.00   $233.00  
  Purchase #3 $47.31   7.691%   $50.9486   $50.95   $50.95   $50.90  
  Purchase #4 $192.32   11.439%   $214.3195   $214.32   $214.30   $214.30  
  Purchase #5 $141.86   8.863%   $154.4331   $154.43   $154.45   $154.40  
  Purchase #6 $109.40   5.465%   $115.3787   $115.38   $115.40   $115.40  
  Purchase #7 $84.48   11.744%   $94.4013   $94.40   $94.40   $94.40  
  7 purchase totals = $1,024.74       $1,107.6727   $1,107.67   $1,107.70   $1,107.60