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 $196.96   10.691%   $218.017   $218.02   $218.00   $218.00  
  Purchase #2 $233.51   12.395%   $262.4536   $262.45   $262.45   $262.50  
  Purchase #3 $15.79   7.165%   $16.9214   $16.92   $16.90   $16.90  
  Purchase #4 $107.79   7.613%   $115.9961   $116.00   $116.00   $116.00  
  Purchase #5 $192.55   13.445%   $218.4383   $218.44   $218.45   $218.40  
  Purchase #6 $183.66   13.607%   $208.6506   $208.65   $208.65   $208.70  
  Purchase #7 $30.73   12.410%   $34.5436   $34.54   $34.55   $34.50  
  7 purchase totals = $960.99       $1,075.0206   $1,075.02   $1,075.00   $1,075.00