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 $197.41   10.202%   $217.5498   $217.55   $217.55   $217.50  
  Purchase #2 $248.47   8.139%   $268.693   $268.69   $268.70   $268.70  
  Purchase #3 $249.46   6.225%   $264.9889   $264.99   $265.00   $265.00  
  Purchase #4 $77.69   6.325%   $82.6039   $82.60   $82.60   $82.60  
  Purchase #5 $5.67   4.114%   $5.9033   $5.90   $5.90   $5.90  
  Purchase #6 $118.91   10.414%   $131.2933   $131.29   $131.30   $131.30  
  Purchase #7 $232.93   9.345%   $254.6973   $254.70   $254.70   $254.70  
  7 purchase totals = $1,130.54       $1,225.7295   $1,225.72   $1,225.75   $1,225.70