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 $222.63   4.754%   $233.2138   $233.21   $233.20   $233.20  
  Purchase #2 $175.96   5.500%   $185.6378   $185.64   $185.65   $185.60  
  Purchase #3 $217.97   5.552%   $230.0717   $230.07   $230.05   $230.10  
  Purchase #4 $43.46   7.873%   $46.8816   $46.88   $46.90   $46.90  
  Purchase #5 $215.35   7.335%   $231.1459   $231.15   $231.15   $231.10  
  Purchase #6 $114.93   4.588%   $120.203   $120.20   $120.20   $120.20  
  Purchase #7 $172.56   12.724%   $194.5165   $194.52   $194.50   $194.50  
  7 purchase totals = $1,162.86       $1,241.6703   $1,241.67   $1,241.65   $1,241.60