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 $57.53   8.562%   $62.4557   $62.46   $62.45   $62.50  
  Purchase #2 $95.97   10.130%   $105.6918   $105.69   $105.70   $105.70  
  Purchase #3 $243.42   7.241%   $261.046   $261.05   $261.05   $261.00  
  Purchase #4 $13.39   6.598%   $14.2735   $14.27   $14.25   $14.30  
  Purchase #5 $182.38   5.411%   $192.2486   $192.25   $192.25   $192.20  
  Purchase #6 $144.41   6.365%   $153.6017   $153.60   $153.60   $153.60  
  Purchase #7 $89.79   8.526%   $97.4455   $97.45   $97.45   $97.40  
  7 purchase totals = $826.89       $886.7628   $886.77   $886.75   $886.70