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 $47.46   4.465%   $49.5791   $49.58   $49.60   $49.60  
  Purchase #2 $210.76   8.423%   $228.5123   $228.51   $228.50   $228.50  
  Purchase #3 $248.45   8.547%   $269.685   $269.69   $269.70   $269.70  
  Purchase #4 $61.98   8.250%   $67.0934   $67.09   $67.10   $67.10  
  Purchase #5 $168.61   5.559%   $177.983   $177.98   $178.00   $178.00  
  Purchase #6 $50.37   6.410%   $53.5987   $53.60   $53.60   $53.60  
  Purchase #7 $197.90   3.856%   $205.531   $205.53   $205.55   $205.50  
  7 purchase totals = $985.53       $1,051.9825   $1,051.98   $1,052.05   $1,052.00