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	$36.50	13.423%	$41.3994	$41.40	$41.40	$41.40
Purchase #2	$106.88	5.115%	$112.3469	$112.35	$112.35	$112.30
Purchase #3	$166.39	4.202%	$173.3817	$173.38	$173.40	$173.40
Purchase #4	$36.64	6.682%	$39.0883	$39.09	$39.10	$39.10
Purchase #5	$172.94	13.805%	$196.8144	$196.81	$196.80	$196.80
Purchase #6	$189.47	4.636%	$198.2538	$198.25	$198.25	$198.30
Purchase #7	$14.39	3.274%	$14.8611	$14.86	$14.85	$14.90
7 purchase totals =	$723.21		$776.1456	$776.14	$776.15	$776.20