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 $184.93   8.696%   $201.0115   $201.01   $201.00   $201.00  
  Purchase #2 $51.64   10.416%   $57.0188   $57.02   $57.00   $57.00  
  Purchase #3 $33.99   4.242%   $35.4319   $35.43   $35.45   $35.40  
  Purchase #4 $218.81   6.355%   $232.7154   $232.72   $232.70   $232.70  
  Purchase #5 $118.76   10.410%   $131.1229   $131.12   $131.10   $131.10  
  Purchase #6 $105.81   8.365%   $114.661   $114.66   $114.65   $114.70  
  Purchase #7 $249.98   10.676%   $276.6679   $276.67   $276.65   $276.70  
  7 purchase totals = $963.92       $1,048.6294   $1,048.63   $1,048.55   $1,048.60