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 $33.26   4.358%   $34.7095   $34.71   $34.70   $34.70  
  Purchase #2 $48.79   10.327%   $53.8285   $53.83   $53.85   $53.80  
  Purchase #3 $221.62   6.160%   $235.2718   $235.27   $235.25   $235.30  
  Purchase #4 $60.48   3.745%   $62.745   $62.75   $62.75   $62.70  
  Purchase #5 $67.89   5.181%   $71.4074   $71.41   $71.40   $71.40  
  Purchase #6 $191.64   7.404%   $205.829   $205.83   $205.85   $205.80  
  Purchase #7 $57.68   4.129%   $60.0616   $60.06   $60.05   $60.10  
  7 purchase totals = $681.36       $723.8528   $723.86   $723.85   $723.80