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 $216.76   10.538%   $239.6022   $239.60   $239.60   $239.60  
  Purchase #2 $53.62   3.110%   $55.2876   $55.29   $55.30   $55.30  
  Purchase #3 $66.45   10.209%   $73.2339   $73.23   $73.25   $73.20  
  Purchase #4 $145.38   11.611%   $162.2601   $162.26   $162.25   $162.30  
  Purchase #5 $213.35   6.500%   $227.2178   $227.22   $227.20   $227.20  
  Purchase #6 $206.53   3.605%   $213.9754   $213.98   $214.00   $214.00  
  Purchase #7 $92.37   5.534%   $97.4818   $97.48   $97.50   $97.50  
  7 purchase totals = $994.46       $1,069.0588   $1,069.06   $1,069.10   $1,069.10