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 $85.60   13.634%   $97.2707   $97.27   $97.25   $97.30  
  Purchase #2 $182.69   7.651%   $196.6676   $196.67   $196.65   $196.70  
  Purchase #3 $232.47   3.728%   $241.1365   $241.14   $241.15   $241.10  
  Purchase #4 $236.36   9.525%   $258.8733   $258.87   $258.85   $258.90  
  Purchase #5 $232.66   8.638%   $252.7572   $252.76   $252.75   $252.80  
  Purchase #6 $62.93   7.114%   $67.4068   $67.41   $67.40   $67.40  
  Purchase #7 $76.39   5.285%   $80.4272   $80.43   $80.45   $80.40  
  7 purchase totals = $1,109.10       $1,194.5393   $1,194.55   $1,194.50   $1,194.60