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 $76.49   13.658%   $86.937   $86.94   $86.95   $86.90  
  Purchase #2 $226.97   12.560%   $255.4774   $255.48   $255.50   $255.50  
  Purchase #3 $206.30   12.522%   $232.1329   $232.13   $232.15   $232.10  
  Purchase #4 $126.87   10.844%   $140.6278   $140.63   $140.65   $140.60  
  Purchase #5 $234.90   6.371%   $249.8655   $249.87   $249.85   $249.90  
  Purchase #6 $198.71   11.254%   $221.0728   $221.07   $221.05   $221.10  
  Purchase #7 $124.25   8.216%   $134.4584   $134.46   $134.45   $134.50  
  7 purchase totals = $1,194.49       $1,320.5718   $1,320.58   $1,320.60   $1,320.60