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	$137.50	5.820%	$145.5025	$145.50	$145.50	$145.50
Purchase #2	$98.32	9.861%	$108.0153	$108.02	$108.00	$108.00
Purchase #3	$49.55	9.379%	$54.1973	$54.20	$54.20	$54.20
Purchase #4	$62.55	4.765%	$65.5305	$65.53	$65.55	$65.50
Purchase #5	$174.38	6.789%	$186.2187	$186.22	$186.20	$186.20
Purchase #6	$106.50	4.309%	$111.0891	$111.09	$111.10	$111.10
Purchase #7	$10.61	10.665%	$11.7416	$11.74	$11.75	$11.70
7 purchase totals =	$639.41		$682.2950	$682.30	$682.30	$682.20