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 $86.71   10.645%   $95.9403   $95.94   $95.95   $95.90  
  Purchase #2 $242.42   10.811%   $268.628   $268.63   $268.65   $268.60  
  Purchase #3 $51.82   6.723%   $55.3039   $55.30   $55.30   $55.30  
  Purchase #4 $192.31   13.853%   $218.9507   $218.95   $218.95   $219.00  
  Purchase #5 $153.77   8.764%   $167.2464   $167.25   $167.25   $167.20  
  Purchase #6 $94.83   3.478%   $98.1282   $98.13   $98.15   $98.10  
  Purchase #7 $75.66   3.332%   $78.181   $78.18   $78.20   $78.20  
  7 purchase totals = $897.52       $982.3785   $982.38   $982.45   $982.30