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 $104.82   8.798%   $114.0421   $114.04   $114.05   $114.00  
  Purchase #2 $135.48   13.549%   $153.8362   $153.84   $153.85   $153.80  
  Purchase #3 $214.73   3.639%   $222.544   $222.54   $222.55   $222.50  
  Purchase #4 $126.65   11.863%   $141.6745   $141.67   $141.65   $141.70  
  Purchase #5 $190.39   5.393%   $200.6577   $200.66   $200.65   $200.70  
  Purchase #6 $164.64   8.432%   $178.5224   $178.52   $178.50   $178.50  
  Purchase #7 $174.92   8.466%   $189.7287   $189.73   $189.75   $189.70  
  7 purchase totals = $1,111.63       $1,201.0056   $1,201.00   $1,201.00   $1,200.90