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 $63.62   13.233%   $72.0388   $72.04   $72.05   $72.00  
  Purchase #2 $250.69   5.722%   $265.0345   $265.03   $265.05   $265.00  
  Purchase #3 $143.47   5.674%   $151.6105   $151.61   $151.60   $151.60  
  Purchase #4 $247.31   9.552%   $270.9331   $270.93   $270.95   $270.90  
  Purchase #5 $32.25   9.363%   $35.2696   $35.27   $35.25   $35.30  
  Purchase #6 $182.37   3.367%   $188.5104   $188.51   $188.50   $188.50  
  Purchase #7 $197.33   11.794%   $220.6031   $220.60   $220.60   $220.60  
  7 purchase totals = $1,117.04       $1,204.0000   $1,203.99   $1,204.00   $1,203.90