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 $215.79   6.108%   $228.9705   $228.97   $228.95   $229.00  
  Purchase #2 $233.37   11.119%   $259.3184   $259.32   $259.30   $259.30  
  Purchase #3 $167.25   4.690%   $175.094   $175.09   $175.10   $175.10  
  Purchase #4 $182.54   5.286%   $192.1891   $192.19   $192.20   $192.20  
  Purchase #5 $63.71   10.537%   $70.4231   $70.42   $70.40   $70.40  
  Purchase #6 $194.83   7.459%   $209.3624   $209.36   $209.35   $209.40  
  Purchase #7 $208.43   7.426%   $223.908   $223.91   $223.90   $223.90  
  7 purchase totals = $1,265.92       $1,359.2655   $1,359.26   $1,359.20   $1,359.30