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	$147.32	7.626%	$158.5546	$158.55	$158.55	$158.60
Purchase #2	$203.34	11.258%	$226.232	$226.23	$226.25	$226.20
Purchase #3	$11.30	10.654%	$12.5039	$12.50	$12.50	$12.50
Purchase #4	$195.50	4.427%	$204.1548	$204.15	$204.15	$204.20
Purchase #5	$178.56	6.568%	$190.2878	$190.29	$190.30	$190.30
Purchase #6	$97.49	8.492%	$105.7689	$105.77	$105.75	$105.80
Purchase #7	$149.52	12.756%	$168.5928	$168.59	$168.60	$168.60
7 purchase totals =	$983.03		$1,066.0948	$1,066.08	$1,066.10	$1,066.20