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 $208.99   6.615%   $222.8147   $222.81   $222.80   $222.80  
  Purchase #2 $41.48   4.141%   $43.1977   $43.20   $43.20   $43.20  
  Purchase #3 $129.25   11.370%   $143.9457   $143.95   $143.95   $143.90  
  Purchase #4 $173.65   12.459%   $195.2851   $195.29   $195.30   $195.30  
  Purchase #5 $92.98   5.359%   $97.9628   $97.96   $97.95   $98.00  
  Purchase #6 $239.61   12.469%   $269.487   $269.49   $269.50   $269.50  
  Purchase #7 $199.87   3.698%   $207.2612   $207.26   $207.25   $207.30  
  7 purchase totals = $1,085.83       $1,179.9542   $1,179.96   $1,179.95   $1,180.00