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 $182.77   9.330%   $199.8224   $199.82   $199.80   $199.80  
  Purchase #2 $242.36   8.388%   $262.6892   $262.69   $262.70   $262.70  
  Purchase #3 $40.50   4.186%   $42.1953   $42.20   $42.20   $42.20  
  Purchase #4 $236.95   9.161%   $258.657   $258.66   $258.65   $258.70  
  Purchase #5 $224.56   13.258%   $254.3322   $254.33   $254.35   $254.30  
  Purchase #6 $189.54   8.375%   $205.414   $205.41   $205.40   $205.40  
  Purchase #7 $105.99   3.391%   $109.5841   $109.58   $109.60   $109.60  
  7 purchase totals = $1,222.67       $1,332.6942   $1,332.69   $1,332.70   $1,332.70