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	$206.26	6.864%	$220.4177	$220.42	$220.40	$220.40
Purchase #2	$39.55	9.425%	$43.2776	$43.28	$43.30	$43.30
Purchase #3	$41.48	3.416%	$42.897	$42.90	$42.90	$42.90
Purchase #4	$164.31	3.512%	$170.0806	$170.08	$170.10	$170.10
Purchase #5	$51.28	5.483%	$54.0917	$54.09	$54.10	$54.10
Purchase #6	$139.75	3.670%	$144.8788	$144.88	$144.90	$144.90
Purchase #7	$196.63	4.472%	$205.4233	$205.42	$205.40	$205.40
7 purchase totals =	$839.26		$881.0667	$881.07	$881.10	$881.10