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 $60.76   3.637%   $62.9698   $62.97   $62.95   $63.00  
  Purchase #2 $213.81   13.476%   $242.623   $242.62   $242.60   $242.60  
  Purchase #3 $46.29   5.821%   $48.9845   $48.98   $49.00   $49.00  
  Purchase #4 $136.87   5.517%   $144.4211   $144.42   $144.40   $144.40  
  Purchase #5 $152.79   10.199%   $168.3731   $168.37   $168.35   $168.40  
  Purchase #6 $187.49   11.136%   $208.3689   $208.37   $208.35   $208.40  
  Purchase #7 $151.45   5.328%   $159.5193   $159.52   $159.50   $159.50  
  7 purchase totals = $949.46       $1,035.2597   $1,035.25   $1,035.15   $1,035.30