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 $196.99   5.599%   $208.0195   $208.02   $208.00   $208.00  
  Purchase #2 $102.97   11.366%   $114.6736   $114.67   $114.65   $114.70  
  Purchase #3 $250.53   8.206%   $271.0885   $271.09   $271.10   $271.10  
  Purchase #4 $105.43   4.267%   $109.9287   $109.93   $109.95   $109.90  
  Purchase #5 $173.48   8.416%   $188.0801   $188.08   $188.10   $188.10  
  Purchase #6 $155.90   8.778%   $169.5849   $169.58   $169.60   $169.60  
  Purchase #7 $39.26   12.174%   $44.0395   $44.04   $44.05   $44.00  
  7 purchase totals = $1,024.56       $1,105.4148   $1,105.41   $1,105.45   $1,105.40