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	$165.95	13.829%	$188.8992	$188.90	$188.90	$188.90
Purchase #2	$102.50	8.736%	$111.4544	$111.45	$111.45	$111.50
Purchase #3	$162.74	7.346%	$174.6949	$174.69	$174.70	$174.70
Purchase #4	$143.91	7.504%	$154.709	$154.71	$154.70	$154.70
Purchase #5	$171.84	6.552%	$183.099	$183.10	$183.10	$183.10
Purchase #6	$190.77	10.624%	$211.0374	$211.04	$211.05	$211.00
Purchase #7	$68.26	6.383%	$72.617	$72.62	$72.60	$72.60
7 purchase totals =	$1,005.97		$1,096.5109	$1,096.51	$1,096.50	$1,096.50