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 $36.49   13.554%   $41.4359   $41.44   $41.45   $41.40  
  Purchase #2 $225.42   3.363%   $233.0009   $233.00   $233.00   $233.00  
  Purchase #3 $8.66   4.750%   $9.0714   $9.07   $9.05   $9.10  
  Purchase #4 $43.48   13.863%   $49.5076   $49.51   $49.50   $49.50  
  Purchase #5 $217.58   13.779%   $247.5603   $247.56   $247.55   $247.60  
  Purchase #6 $248.64   10.498%   $274.7422   $274.74   $274.75   $274.70  
  Purchase #7 $88.65   4.278%   $92.4424   $92.44   $92.45   $92.40  
  7 purchase totals = $868.92       $947.7607   $947.76   $947.75   $947.70