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 $163.81   8.522%   $177.7699   $177.77   $177.75   $177.80  
  Purchase #2 $247.93   4.445%   $258.9505   $258.95   $258.95   $259.00  
  Purchase #3 $207.85   4.213%   $216.6067   $216.61   $216.60   $216.60  
  Purchase #4 $186.39   5.540%   $196.716   $196.72   $196.70   $196.70  
  Purchase #5 $185.30   10.680%   $205.09   $205.09   $205.10   $205.10  
  Purchase #6 $106.49   5.540%   $112.3895   $112.39   $112.40   $112.40  
  Purchase #7 $26.26   10.420%   $28.9963   $29.00   $29.00   $29.00  
  7 purchase totals = $1,124.03       $1,196.5189   $1,196.53   $1,196.50   $1,196.60