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	$205.35	12.232%	$230.4684	$230.47	$230.45	$230.50
Purchase #2	$211.27	4.490%	$220.756	$220.76	$220.75	$220.80
Purchase #3	$151.26	4.859%	$158.6097	$158.61	$158.60	$158.60
Purchase #4	$24.62	5.265%	$25.9162	$25.92	$25.90	$25.90
Purchase #5	$99.78	3.146%	$102.9191	$102.92	$102.90	$102.90
Purchase #6	$233.37	9.730%	$256.0769	$256.08	$256.10	$256.10
Purchase #7	$100.71	4.586%	$105.3286	$105.33	$105.35	$105.30
7 purchase totals =	$1,026.36		$1,100.0749	$1,100.09	$1,100.05	$1,100.10