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 $62.81   9.792%   $68.9604   $68.96   $68.95   $69.00  
  Purchase #2 $97.43   7.745%   $104.976   $104.98   $105.00   $105.00  
  Purchase #3 $123.63   4.512%   $129.2082   $129.21   $129.20   $129.20  
  Purchase #4 $227.25   12.307%   $255.2177   $255.22   $255.20   $255.20  
  Purchase #5 $156.49   11.332%   $174.2234   $174.22   $174.20   $174.20  
  Purchase #6 $173.86   7.298%   $186.5483   $186.55   $186.55   $186.50  
  Purchase #7 $72.58   6.187%   $77.0705   $77.07   $77.05   $77.10  
  7 purchase totals = $914.05       $996.2045   $996.21   $996.15   $996.20