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	$100.51	12.136%	$112.7079	$112.71	$112.70	$112.70
Purchase #2	$61.32	10.333%	$67.6562	$67.66	$67.65	$67.70
Purchase #3	$106.60	11.370%	$118.7204	$118.72	$118.70	$118.70
Purchase #4	$240.79	10.645%	$266.4221	$266.42	$266.40	$266.40
Purchase #5	$138.77	12.229%	$155.7402	$155.74	$155.75	$155.70
Purchase #6	$139.61	8.448%	$151.4043	$151.40	$151.40	$151.40
Purchase #7	$158.55	4.321%	$165.4009	$165.40	$165.40	$165.40
7 purchase totals =	$946.15		$1,038.0520	$1,038.05	$1,038.00	$1,038.00