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 $62.25   11.846%   $69.6241   $69.62   $69.60   $69.60  
  Purchase #2 $190.27   10.491%   $210.2312   $210.23   $210.25   $210.20  
  Purchase #3 $63.99   11.521%   $71.3623   $71.36   $71.35   $71.40  
  Purchase #4 $216.82   12.664%   $244.2781   $244.28   $244.30   $244.30  
  Purchase #5 $238.42   4.634%   $249.4684   $249.47   $249.45   $249.50  
  Purchase #6 $177.91   7.224%   $190.7622   $190.76   $190.75   $190.80  
  Purchase #7 $36.86   3.291%   $38.0731   $38.07   $38.05   $38.10  
  7 purchase totals = $986.52       $1,073.7994   $1,073.79   $1,073.75   $1,073.90