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 $86.41   8.269%   $93.5552   $93.56   $93.55   $93.60  
  Purchase #2 $15.35   3.811%   $15.935   $15.94   $15.95   $15.90  
  Purchase #3 $46.95   13.458%   $53.2685   $53.27   $53.25   $53.30  
  Purchase #4 $46.45   5.299%   $48.9114   $48.91   $48.90   $48.90  
  Purchase #5 $79.33   11.202%   $88.2165   $88.22   $88.20   $88.20  
  Purchase #6 $89.50   8.589%   $97.1872   $97.19   $97.20   $97.20  
  Purchase #7 $75.98   10.616%   $84.046   $84.05   $84.05   $84.00  
  7 purchase totals = $439.97       $481.1198   $481.14   $481.10   $481.10