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 $38.75   12.404%   $43.5566   $43.56   $43.55   $43.60  
  Purchase #2 $241.81   12.291%   $271.5309   $271.53   $271.55   $271.50  
  Purchase #3 $135.44   5.213%   $142.5005   $142.50   $142.50   $142.50  
  Purchase #4 $231.58   4.395%   $241.7579   $241.76   $241.75   $241.80  
  Purchase #5 $41.79   4.491%   $43.6668   $43.67   $43.65   $43.70  
  Purchase #6 $201.75   11.509%   $224.9694   $224.97   $224.95   $225.00  
  Purchase #7 $214.53   5.605%   $226.5544   $226.55   $226.55   $226.60  
  7 purchase totals = $1,105.65       $1,194.5365   $1,194.54   $1,194.50   $1,194.70