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 $113.78   10.261%   $125.455   $125.46   $125.45   $125.50  
  Purchase #2 $159.26   3.132%   $164.248   $164.25   $164.25   $164.20  
  Purchase #3 $39.89   12.493%   $44.8735   $44.87   $44.85   $44.90  
  Purchase #4 $191.60   7.478%   $205.9278   $205.93   $205.95   $205.90  
  Purchase #5 $179.76   3.299%   $185.6903   $185.69   $185.70   $185.70  
  Purchase #6 $175.92   3.615%   $182.2795   $182.28   $182.30   $182.30  
  Purchase #7 $103.94   10.612%   $114.9701   $114.97   $114.95   $115.00  
  7 purchase totals = $964.15       $1,023.4442   $1,023.45   $1,023.45   $1,023.50