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 $44.57   5.126%   $46.8547   $46.85   $46.85   $46.90  
  Purchase #2 $127.65   11.356%   $142.1459   $142.15   $142.15   $142.10  
  Purchase #3 $58.71   9.244%   $64.1372   $64.14   $64.15   $64.10  
  Purchase #4 $241.30   11.483%   $269.0085   $269.01   $269.00   $269.00  
  Purchase #5 $40.71   5.545%   $42.9674   $42.97   $42.95   $43.00  
  Purchase #6 $215.97   11.242%   $240.2493   $240.25   $240.25   $240.20  
  Purchase #7 $245.60   7.678%   $264.4572   $264.46   $264.45   $264.50  
  7 purchase totals = $974.51       $1,069.8202   $1,069.83   $1,069.80   $1,069.80