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 $224.41   8.852%   $244.2748   $244.27   $244.25   $244.30  
  Purchase #2 $98.93   11.237%   $110.0468   $110.05   $110.05   $110.00  
  Purchase #3 $174.70   11.106%   $194.1022   $194.10   $194.10   $194.10  
  Purchase #4 $97.59   4.391%   $101.8752   $101.88   $101.90   $101.90  
  Purchase #5 $119.75   6.577%   $127.626   $127.63   $127.65   $127.60  
  Purchase #6 $162.76   6.741%   $173.7317   $173.73   $173.75   $173.70  
  Purchase #7 $185.31   11.387%   $206.4112   $206.41   $206.40   $206.40  
  7 purchase totals = $1,063.45       $1,158.0679   $1,158.07   $1,158.10   $1,158.00