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	$111.67	4.550%	$116.751	$116.75	$116.75	$116.80
Purchase #2	$107.42	12.311%	$120.6445	$120.64	$120.65	$120.60
Purchase #3	$103.99	7.586%	$111.8787	$111.88	$111.90	$111.90
Purchase #4	$46.58	10.104%	$51.2864	$51.29	$51.30	$51.30
Purchase #5	$149.93	5.665%	$158.4235	$158.42	$158.40	$158.40
Purchase #6	$23.57	3.318%	$24.3521	$24.35	$24.35	$24.40
Purchase #7	$40.96	3.133%	$42.2433	$42.24	$42.25	$42.20
7 purchase totals =	$584.12		$625.5795	$625.57	$625.60	$625.60