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 $108.84   5.293%   $114.6009   $114.60   $114.60   $114.60  
  Purchase #2 $23.99   5.740%   $25.367   $25.37   $25.35   $25.40  
  Purchase #3 $117.88   8.469%   $127.8633   $127.86   $127.85   $127.90  
  Purchase #4 $111.40   5.316%   $117.322   $117.32   $117.30   $117.30  
  Purchase #5 $152.81   7.754%   $164.6589   $164.66   $164.65   $164.70  
  Purchase #6 $110.88   10.247%   $122.2419   $122.24   $122.25   $122.20  
  Purchase #7 $242.93   10.281%   $267.9056   $267.91   $267.90   $267.90  
  7 purchase totals = $868.73       $939.9596   $939.96   $939.90   $940.00