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 $182.33   7.623%   $196.229   $196.23   $196.25   $196.20  
  Purchase #2 $52.66   3.868%   $54.6969   $54.70   $54.70   $54.70  
  Purchase #3 $59.43   9.178%   $64.8845   $64.88   $64.90   $64.90  
  Purchase #4 $247.71   5.853%   $262.2085   $262.21   $262.20   $262.20  
  Purchase #5 $121.59   11.193%   $135.1996   $135.20   $135.20   $135.20  
  Purchase #6 $15.52   8.300%   $16.8082   $16.81   $16.80   $16.80  
  Purchase #7 $153.94   9.166%   $168.0501   $168.05   $168.05   $168.10  
  7 purchase totals = $833.18       $898.0768   $898.08   $898.10   $898.10