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	$55.43	7.105%	$59.3683	$59.37	$59.35	$59.40
Purchase #2	$45.62	13.205%	$51.6441	$51.64	$51.65	$51.60
Purchase #3	$42.27	7.569%	$45.4694	$45.47	$45.45	$45.50
Purchase #4	$62.46	9.286%	$68.26	$68.26	$68.25	$68.30
Purchase #5	$231.83	13.827%	$263.8851	$263.89	$263.90	$263.90
Purchase #6	$93.67	5.792%	$99.0954	$99.10	$99.10	$99.10
Purchase #7	$42.85	13.311%	$48.5538	$48.55	$48.55	$48.60
7 purchase totals =	$574.13		$636.2761	$636.28	$636.25	$636.40