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 $162.47   6.847%   $173.5943   $173.59   $173.60   $173.60  
  Purchase #2 $208.66   4.381%   $217.8014   $217.80   $217.80   $217.80  
  Purchase #3 $107.42   3.119%   $110.7704   $110.77   $110.75   $110.80  
  Purchase #4 $210.49   6.626%   $224.4371   $224.44   $224.45   $224.40  
  Purchase #5 $225.55   5.722%   $238.456   $238.46   $238.45   $238.50  
  Purchase #6 $51.65   3.780%   $53.6024   $53.60   $53.60   $53.60  
  Purchase #7 $167.32   12.216%   $187.7598   $187.76   $187.75   $187.80  
  7 purchase totals = $1,133.56       $1,206.4214   $1,206.42   $1,206.40   $1,206.50