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 $84.37   12.702%   $95.0867   $95.09   $95.10   $95.10  
  Purchase #2 $171.53   12.782%   $193.455   $193.46   $193.45   $193.50  
  Purchase #3 $115.68   12.675%   $130.3424   $130.34   $130.35   $130.30  
  Purchase #4 $150.85   4.557%   $157.7242   $157.72   $157.70   $157.70  
  Purchase #5 $222.66   13.337%   $252.3562   $252.36   $252.35   $252.40  
  Purchase #6 $194.87   9.495%   $213.3729   $213.37   $213.35   $213.40  
  Purchase #7 $111.76   10.296%   $123.2668   $123.27   $123.25   $123.30  
  7 purchase totals = $1,051.72       $1,165.6042   $1,165.61   $1,165.55   $1,165.70