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 $195.73   5.244%   $205.9941   $205.99   $206.00   $206.00  
  Purchase #2 $76.28   7.234%   $81.7981   $81.80   $81.80   $81.80  
  Purchase #3 $153.95   3.225%   $158.9149   $158.91   $158.90   $158.90  
  Purchase #4 $226.33   3.798%   $234.926   $234.93   $234.95   $234.90  
  Purchase #5 $176.86   8.697%   $192.2415   $192.24   $192.25   $192.20  
  Purchase #6 $13.46   7.467%   $14.4651   $14.47   $14.45   $14.50  
  Purchase #7 $212.63   8.823%   $231.3903   $231.39   $231.40   $231.40  
  7 purchase totals = $1,055.24       $1,119.7300   $1,119.73   $1,119.75   $1,119.70