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 $242.29   5.105%   $254.6589   $254.66   $254.65   $254.70  
  Purchase #2 $22.73   5.786%   $24.0452   $24.05   $24.05   $24.00  
  Purchase #3 $230.68   4.821%   $241.8011   $241.80   $241.80   $241.80  
  Purchase #4 $225.76   3.413%   $233.4652   $233.47   $233.45   $233.50  
  Purchase #5 $32.36   6.388%   $34.4272   $34.43   $34.45   $34.40  
  Purchase #6 $230.70   4.625%   $241.3699   $241.37   $241.35   $241.40  
  Purchase #7 $209.27   5.430%   $220.6334   $220.63   $220.65   $220.60  
  7 purchase totals = $1,193.79       $1,250.4009   $1,250.41   $1,250.40   $1,250.40