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	$222.48	7.677%	$239.5598	$239.56	$239.55	$239.60
Purchase #2	$105.41	5.346%	$111.0452	$111.05	$111.05	$111.00
Purchase #3	$167.81	10.295%	$185.086	$185.09	$185.10	$185.10
Purchase #4	$223.40	4.865%	$234.2684	$234.27	$234.25	$234.30
Purchase #5	$48.63	8.259%	$52.6464	$52.65	$52.65	$52.60
Purchase #6	$114.79	3.279%	$118.554	$118.55	$118.55	$118.60
Purchase #7	$183.43	8.277%	$198.6125	$198.61	$198.60	$198.60
7 purchase totals =	$1,065.95		$1,139.7723	$1,139.78	$1,139.75	$1,139.80