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	$174.91	13.337%	$198.2377	$198.24	$198.25	$198.20
Purchase #2	$95.64	3.380%	$98.8726	$98.87	$98.85	$98.90
Purchase #3	$144.71	9.243%	$158.0855	$158.09	$158.10	$158.10
Purchase #4	$57.50	8.369%	$62.3122	$62.31	$62.30	$62.30
Purchase #5	$38.69	5.413%	$40.7843	$40.78	$40.80	$40.80
Purchase #6	$121.70	4.451%	$127.1169	$127.12	$127.10	$127.10
Purchase #7	$94.75	3.874%	$98.4206	$98.42	$98.40	$98.40
7 purchase totals =	$727.90		$783.8298	$783.83	$783.80	$783.80