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 $188.95   3.159%   $194.9189   $194.92   $194.90   $194.90  
  Purchase #2 $193.73   3.130%   $199.7937   $199.79   $199.80   $199.80  
  Purchase #3 $178.44   6.713%   $190.4187   $190.42   $190.40   $190.40  
  Purchase #4 $44.73   4.405%   $46.7004   $46.70   $46.70   $46.70  
  Purchase #5 $119.83   5.605%   $126.5465   $126.55   $126.55   $126.50  
  Purchase #6 $69.43   3.109%   $71.5886   $71.59   $71.60   $71.60  
  Purchase #7 $248.42   8.318%   $269.0836   $269.08   $269.10   $269.10  
  7 purchase totals = $1,043.53       $1,099.0504   $1,099.05   $1,099.05   $1,099.00