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 $208.61   5.103%   $219.2554   $219.26   $219.25   $219.30  
  Purchase #2 $95.56   10.323%   $105.4247   $105.42   $105.40   $105.40  
  Purchase #3 $13.95   11.692%   $15.581   $15.58   $15.60   $15.60  
  Purchase #4 $71.83   13.630%   $81.6204   $81.62   $81.60   $81.60  
  Purchase #5 $202.65   5.723%   $214.2477   $214.25   $214.25   $214.20  
  Purchase #6 $78.61   5.580%   $82.9964   $83.00   $83.00   $83.00  
  Purchase #7 $193.55   10.599%   $214.0644   $214.06   $214.05   $214.10  
  7 purchase totals = $864.76       $933.1900   $933.19   $933.15   $933.20