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 $205.61   13.467%   $233.2995   $233.30   $233.30   $233.30  
  Purchase #2 $96.36   9.178%   $105.2039   $105.20   $105.20   $105.20  
  Purchase #3 $22.61   6.121%   $23.994   $23.99   $24.00   $24.00  
  Purchase #4 $164.94   12.491%   $185.5427   $185.54   $185.55   $185.50  
  Purchase #5 $182.95   8.823%   $199.0917   $199.09   $199.10   $199.10  
  Purchase #6 $157.37   8.205%   $170.2822   $170.28   $170.30   $170.30  
  Purchase #7 $159.68   5.217%   $168.0105   $168.01   $168.00   $168.00  
  7 purchase totals = $989.52       $1,085.4245   $1,085.41   $1,085.45   $1,085.40