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 $103.65   10.568%   $114.6037   $114.60   $114.60   $114.60  
  Purchase #2 $134.83   3.614%   $139.7028   $139.70   $139.70   $139.70  
  Purchase #3 $55.38   11.258%   $61.6147   $61.61   $61.60   $61.60  
  Purchase #4 $91.73   11.411%   $102.1973   $102.20   $102.20   $102.20  
  Purchase #5 $43.59   7.217%   $46.7359   $46.74   $46.75   $46.70  
  Purchase #6 $118.72   13.678%   $134.9585   $134.96   $134.95   $135.00  
  Purchase #7 $93.90   4.857%   $98.4607   $98.46   $98.45   $98.50  
  7 purchase totals = $641.80       $698.2736   $698.27   $698.25   $698.30