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 $203.29   5.724%   $214.9263   $214.93   $214.95   $214.90  
  Purchase #2 $55.28   10.259%   $60.9512   $60.95   $60.95   $61.00  
  Purchase #3 $6.38   9.137%   $6.9629   $6.96   $6.95   $7.00  
  Purchase #4 $217.48   3.273%   $224.5981   $224.60   $224.60   $224.60  
  Purchase #5 $198.84   8.251%   $215.2463   $215.25   $215.25   $215.20  
  Purchase #6 $164.98   3.793%   $171.2377   $171.24   $171.25   $171.20  
  Purchase #7 $229.41   12.733%   $258.6208   $258.62   $258.60   $258.60  
  7 purchase totals = $1,075.66       $1,152.5433   $1,152.55   $1,152.55   $1,152.50