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 $208.36   13.619%   $236.7365   $236.74   $236.75   $236.70  
  Purchase #2 $10.27   5.328%   $10.8172   $10.82   $10.80   $10.80  
  Purchase #3 $156.84   9.547%   $171.8135   $171.81   $171.80   $171.80  
  Purchase #4 $213.45   3.859%   $221.687   $221.69   $221.70   $221.70  
  Purchase #5 $37.82   11.854%   $42.3032   $42.30   $42.30   $42.30  
  Purchase #6 $167.52   6.200%   $177.9062   $177.91   $177.90   $177.90  
  Purchase #7 $155.70   5.176%   $163.759   $163.76   $163.75   $163.80  
  7 purchase totals = $949.96       $1,025.0226   $1,025.03   $1,025.00   $1,025.00