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 $215.61   11.204%   $239.7669   $239.77   $239.75   $239.80  
  Purchase #2 $44.61   5.718%   $47.1608   $47.16   $47.15   $47.20  
  Purchase #3 $21.86   5.196%   $22.9958   $23.00   $23.00   $23.00  
  Purchase #4 $200.49   9.806%   $220.15   $220.15   $220.15   $220.20  
  Purchase #5 $193.48   6.166%   $205.41   $205.41   $205.40   $205.40  
  Purchase #6 $190.99   5.565%   $201.6186   $201.62   $201.60   $201.60  
  Purchase #7 $163.86   11.232%   $182.2648   $182.26   $182.25   $182.30  
  7 purchase totals = $1,030.90       $1,119.3669   $1,119.37   $1,119.30   $1,119.50