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 $205.64   4.186%   $214.2481   $214.25   $214.25   $214.20  
  Purchase #2 $182.69   4.159%   $190.2881   $190.29   $190.30   $190.30  
  Purchase #3 $30.66   13.393%   $34.7663   $34.77   $34.75   $34.80  
  Purchase #4 $7.99   6.148%   $8.4812   $8.48   $8.50   $8.50  
  Purchase #5 $228.89   5.874%   $242.335   $242.34   $242.35   $242.30  
  Purchase #6 $158.70   11.330%   $176.6807   $176.68   $176.70   $176.70  
  Purchase #7 $202.40   12.367%   $227.4308   $227.43   $227.45   $227.40  
  7 purchase totals = $1,016.97       $1,094.2302   $1,094.24   $1,094.30   $1,094.20