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 $244.82   8.376%   $265.3261   $265.33   $265.35   $265.30  
  Purchase #2 $196.41   9.413%   $214.8981   $214.90   $214.90   $214.90  
  Purchase #3 $10.37   11.288%   $11.5406   $11.54   $11.55   $11.50  
  Purchase #4 $176.91   10.770%   $195.9632   $195.96   $195.95   $196.00  
  Purchase #5 $197.75   3.195%   $204.0681   $204.07   $204.05   $204.10  
  Purchase #6 $233.32   5.403%   $245.9263   $245.93   $245.95   $245.90  
  Purchase #7 $248.83   3.194%   $256.7776   $256.78   $256.80   $256.80  
  7 purchase totals = $1,308.41       $1,394.5000   $1,394.51   $1,394.55   $1,394.50