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 $33.27   6.785%   $35.5274   $35.53   $35.55   $35.50  
  Purchase #2 $224.25   3.123%   $231.2533   $231.25   $231.25   $231.30  
  Purchase #3 $224.83   8.713%   $244.4194   $244.42   $244.40   $244.40  
  Purchase #4 $116.42   8.723%   $126.5753   $126.58   $126.60   $126.60  
  Purchase #5 $102.71   4.525%   $107.3576   $107.36   $107.35   $107.40  
  Purchase #6 $213.40   13.220%   $241.6115   $241.61   $241.60   $241.60  
  Purchase #7 $71.76   6.856%   $76.6799   $76.68   $76.70   $76.70  
  7 purchase totals = $986.64       $1,063.4244   $1,063.43   $1,063.45   $1,063.50