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 $168.76   8.758%   $183.54   $183.54   $183.55   $183.50  
  Purchase #2 $5.48   9.663%   $6.0095   $6.01   $6.00   $6.00  
  Purchase #3 $152.48   3.589%   $157.9525   $157.95   $157.95   $158.00  
  Purchase #4 $80.75   6.855%   $86.2854   $86.29   $86.30   $86.30  
  Purchase #5 $198.67   5.177%   $208.9551   $208.96   $208.95   $209.00  
  Purchase #6 $164.50   7.320%   $176.5414   $176.54   $176.55   $176.50  
  Purchase #7 $113.31   13.161%   $128.2227   $128.22   $128.20   $128.20  
  7 purchase totals = $883.95       $947.5066   $947.51   $947.50   $947.50