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 $207.52   13.500%   $235.5352   $235.54   $235.55   $235.50  
  Purchase #2 $232.90   12.553%   $262.1359   $262.14   $262.15   $262.10  
  Purchase #3 $218.59   13.581%   $248.2767   $248.28   $248.30   $248.30  
  Purchase #4 $108.29   12.599%   $121.9335   $121.93   $121.95   $121.90  
  Purchase #5 $13.60   4.684%   $14.237   $14.24   $14.25   $14.20  
  Purchase #6 $203.66   12.671%   $229.4658   $229.47   $229.45   $229.50  
  Purchase #7 $46.68   11.431%   $52.016   $52.02   $52.00   $52.00  
  7 purchase totals = $1,031.24       $1,163.6001   $1,163.62   $1,163.65   $1,163.50