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 $183.69   7.116%   $196.7614   $196.76   $196.75   $196.80  
  Purchase #2 $211.32   12.407%   $237.5385   $237.54   $237.55   $237.50  
  Purchase #3 $73.39   10.641%   $81.1994   $81.20   $81.20   $81.20  
  Purchase #4 $42.51   5.305%   $44.7652   $44.77   $44.75   $44.80  
  Purchase #5 $137.88   12.846%   $155.5921   $155.59   $155.60   $155.60  
  Purchase #6 $182.41   6.245%   $193.8015   $193.80   $193.80   $193.80  
  Purchase #7 $93.73   4.187%   $97.6545   $97.65   $97.65   $97.70  
  7 purchase totals = $924.93       $1,007.3126   $1,007.31   $1,007.30   $1,007.40