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 $214.75   4.595%   $224.6178   $224.62   $224.60   $224.60  
  Purchase #2 $11.98   9.733%   $13.146   $13.15   $13.15   $13.10  
  Purchase #3 $13.31   11.786%   $14.8787   $14.88   $14.90   $14.90  
  Purchase #4 $119.82   6.610%   $127.7401   $127.74   $127.75   $127.70  
  Purchase #5 $74.37   6.547%   $79.239   $79.24   $79.25   $79.20  
  Purchase #6 $79.30   6.431%   $84.3998   $84.40   $84.40   $84.40  
  Purchase #7 $190.78   9.547%   $208.9938   $208.99   $209.00   $209.00  
  7 purchase totals = $704.31       $753.0152   $753.02   $753.05   $752.90