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	$57.87	8.546%	$62.8156	$62.82	$62.80	$62.80
Purchase #2	$241.26	5.663%	$254.9226	$254.92	$254.90	$254.90
Purchase #3	$16.47	4.253%	$17.1705	$17.17	$17.15	$17.20
Purchase #4	$70.92	9.514%	$77.6673	$77.67	$77.65	$77.70
Purchase #5	$85.75	4.766%	$89.8368	$89.84	$89.85	$89.80
Purchase #6	$55.64	6.131%	$59.0513	$59.05	$59.05	$59.10
Purchase #7	$228.54	3.730%	$237.0645	$237.06	$237.05	$237.10
7 purchase totals =	$756.45		$798.5286	$798.53	$798.45	$798.60