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 $105.49   8.567%   $114.5273   $114.53   $114.55   $114.50  
  Purchase #2 $238.86   5.702%   $252.4798   $252.48   $252.50   $252.50  
  Purchase #3 $55.87   5.118%   $58.7294   $58.73   $58.75   $58.70  
  Purchase #4 $204.67   11.798%   $228.817   $228.82   $228.80   $228.80  
  Purchase #5 $193.81   4.671%   $202.8629   $202.86   $202.85   $202.90  
  Purchase #6 $61.42   11.286%   $68.3519   $68.35   $68.35   $68.40  
  Purchase #7 $63.56   6.608%   $67.76   $67.76   $67.75   $67.80  
  7 purchase totals = $923.68       $993.5283   $993.53   $993.55   $993.60