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 $104.94   9.361%   $114.7634   $114.76   $114.75   $114.80  
  Purchase #2 $191.77   12.284%   $215.327   $215.33   $215.35   $215.30  
  Purchase #3 $41.32   5.703%   $43.6765   $43.68   $43.70   $43.70  
  Purchase #4 $24.84   8.198%   $26.8764   $26.88   $26.90   $26.90  
  Purchase #5 $107.27   6.255%   $113.9797   $113.98   $114.00   $114.00  
  Purchase #6 $143.98   10.158%   $158.6055   $158.61   $158.60   $158.60  
  Purchase #7 $231.46   13.258%   $262.147   $262.15   $262.15   $262.10  
  7 purchase totals = $845.58       $935.3755   $935.39   $935.45   $935.40