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 $55.81   11.121%   $62.0166   $62.02   $62.00   $62.00  
  Purchase #2 $233.29   12.291%   $261.9637   $261.96   $261.95   $262.00  
  Purchase #3 $123.65   5.252%   $130.1441   $130.14   $130.15   $130.10  
  Purchase #4 $247.93   6.224%   $263.3612   $263.36   $263.35   $263.40  
  Purchase #5 $112.81   5.197%   $118.6727   $118.67   $118.65   $118.70  
  Purchase #6 $190.91   9.254%   $208.5768   $208.58   $208.60   $208.60  
  Purchase #7 $157.51   12.232%   $176.7766   $176.78   $176.80   $176.80  
  7 purchase totals = $1,121.91       $1,221.5117   $1,221.51   $1,221.50   $1,221.60