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 $86.67   9.566%   $94.9609   $94.96   $94.95   $95.00  
  Purchase #2 $145.76   12.832%   $164.4639   $164.46   $164.45   $164.50  
  Purchase #3 $143.47   10.815%   $158.9863   $158.99   $159.00   $159.00  
  Purchase #4 $145.38   12.784%   $163.9654   $163.97   $163.95   $164.00  
  Purchase #5 $76.49   13.458%   $86.784   $86.78   $86.80   $86.80  
  Purchase #6 $116.26   10.858%   $128.8835   $128.88   $128.90   $128.90  
  Purchase #7 $53.55   8.145%   $57.9116   $57.91   $57.90   $57.90  
  7 purchase totals = $767.58       $855.9556   $855.95   $855.95   $856.10