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	$57.62	13.536%	$65.4194	$65.42	$65.40	$65.40
Purchase #2	$12.95	3.177%	$13.3614	$13.36	$13.35	$13.40
Purchase #3	$143.75	10.540%	$158.9013	$158.90	$158.90	$158.90
Purchase #4	$191.98	3.250%	$198.2194	$198.22	$198.20	$198.20
Purchase #5	$102.66	11.635%	$114.6045	$114.60	$114.60	$114.60
Purchase #6	$85.33	8.159%	$92.2921	$92.29	$92.30	$92.30
Purchase #7	$169.98	9.167%	$185.5621	$185.56	$185.55	$185.60
7 purchase totals =	$764.27		$828.3602	$828.35	$828.30	$828.40