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 $185.61   8.616%   $201.6022   $201.60   $201.60   $201.60  
  Purchase #2 $95.36   12.797%   $107.5632   $107.56   $107.55   $107.60  
  Purchase #3 $179.64   12.287%   $201.7124   $201.71   $201.70   $201.70  
  Purchase #4 $159.99   10.481%   $176.7586   $176.76   $176.75   $176.80  
  Purchase #5 $156.70   7.338%   $168.1986   $168.20   $168.20   $168.20  
  Purchase #6 $46.63   12.497%   $52.4574   $52.46   $52.45   $52.50  
  Purchase #7 $5.55   9.377%   $6.0704   $6.07   $6.05   $6.10  
  7 purchase totals = $829.48       $914.3628   $914.36   $914.30   $914.50