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 $84.66   13.344%   $95.957   $95.96   $95.95   $96.00  
  Purchase #2 $182.30   8.178%   $197.2085   $197.21   $197.20   $197.20  
  Purchase #3 $174.44   10.856%   $193.3772   $193.38   $193.40   $193.40  
  Purchase #4 $201.82   10.149%   $222.3027   $222.30   $222.30   $222.30  
  Purchase #5 $99.49   9.492%   $108.9336   $108.93   $108.95   $108.90  
  Purchase #6 $185.72   5.311%   $195.5836   $195.58   $195.60   $195.60  
  Purchase #7 $7.64   3.315%   $7.8933   $7.89   $7.90   $7.90  
  7 purchase totals = $936.07       $1,021.2559   $1,021.25   $1,021.30   $1,021.30