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 $208.75   7.605%   $224.6254   $224.63   $224.65   $224.60  
  Purchase #2 $159.36   3.617%   $165.1241   $165.12   $165.10   $165.10  
  Purchase #3 $65.63   6.636%   $69.9852   $69.99   $70.00   $70.00  
  Purchase #4 $100.51   11.398%   $111.9661   $111.97   $111.95   $112.00  
  Purchase #5 $224.87   11.602%   $250.9594   $250.96   $250.95   $251.00  
  Purchase #6 $113.71   4.251%   $118.5438   $118.54   $118.55   $118.50  
  Purchase #7 $231.64   11.411%   $258.0724   $258.07   $258.05   $258.10  
  7 purchase totals = $1,104.47       $1,199.2764   $1,199.28   $1,199.25   $1,199.30