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 $41.55   3.851%   $43.1501   $43.15   $43.15   $43.20  
  Purchase #2 $193.35   7.182%   $207.2364   $207.24   $207.25   $207.20  
  Purchase #3 $63.62   5.545%   $67.1477   $67.15   $67.15   $67.10  
  Purchase #4 $249.70   13.821%   $284.211   $284.21   $284.20   $284.20  
  Purchase #5 $205.29   4.648%   $214.8319   $214.83   $214.85   $214.80  
  Purchase #6 $134.64   5.441%   $141.9658   $141.97   $141.95   $142.00  
  Purchase #7 $241.76   3.184%   $249.4576   $249.46   $249.45   $249.50  
  7 purchase totals = $1,129.91       $1,208.0005   $1,208.01   $1,208.00   $1,208.00