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	$135.43	9.724%	$148.5992	$148.60	$148.60	$148.60
Purchase #2	$214.84	4.132%	$223.7172	$223.72	$223.70	$223.70
Purchase #3	$40.38	4.443%	$42.1741	$42.17	$42.15	$42.20
Purchase #4	$155.88	3.446%	$161.2516	$161.25	$161.25	$161.30
Purchase #5	$215.76	12.492%	$242.7127	$242.71	$242.70	$242.70
Purchase #6	$151.92	4.180%	$158.2703	$158.27	$158.25	$158.30
Purchase #7	$63.83	7.542%	$68.6441	$68.64	$68.65	$68.60
7 purchase totals =	$978.04		$1,045.3692	$1,045.36	$1,045.30	$1,045.40