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 $32.44   10.225%   $35.757   $35.76   $35.75   $35.80  
  Purchase #2 $234.86   13.671%   $266.9677   $266.97   $266.95   $267.00  
  Purchase #3 $236.36   9.151%   $257.9893   $257.99   $258.00   $258.00  
  Purchase #4 $228.34   12.446%   $256.7592   $256.76   $256.75   $256.80  
  Purchase #5 $207.99   4.781%   $217.934   $217.93   $217.95   $217.90  
  Purchase #6 $186.87   5.649%   $197.4263   $197.43   $197.45   $197.40  
  Purchase #7 $82.81   8.417%   $89.7801   $89.78   $89.80   $89.80  
  7 purchase totals = $1,209.67       $1,322.6136   $1,322.62   $1,322.65   $1,322.70