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 $209.93   5.398%   $221.262   $221.26   $221.25   $221.30  
  Purchase #2 $212.82   13.409%   $241.357   $241.36   $241.35   $241.40  
  Purchase #3 $208.55   10.583%   $230.6208   $230.62   $230.60   $230.60  
  Purchase #4 $221.80   4.289%   $231.313   $231.31   $231.30   $231.30  
  Purchase #5 $184.43   4.724%   $193.1425   $193.14   $193.15   $193.10  
  Purchase #6 $47.95   4.125%   $49.9279   $49.93   $49.95   $49.90  
  Purchase #7 $26.29   8.309%   $28.4744   $28.47   $28.45   $28.50  
  7 purchase totals = $1,111.77       $1,196.0976   $1,196.09   $1,196.05   $1,196.10