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 $144.68   5.743%   $152.989   $152.99   $153.00   $153.00  
  Purchase #2 $107.83   9.119%   $117.663   $117.66   $117.65   $117.70  
  Purchase #3 $62.93   8.586%   $68.3332   $68.33   $68.35   $68.30  
  Purchase #4 $76.97   3.129%   $79.3784   $79.38   $79.40   $79.40  
  Purchase #5 $92.67   6.175%   $98.3924   $98.39   $98.40   $98.40  
  Purchase #6 $235.68   10.307%   $259.9715   $259.97   $259.95   $260.00  
  Purchase #7 $214.53   7.571%   $230.7721   $230.77   $230.75   $230.80  
  7 purchase totals = $935.29       $1,007.4996   $1,007.49   $1,007.50   $1,007.60