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	$143.43	9.215%	$156.6471	$156.65	$156.65	$156.60
Purchase #2	$118.56	8.385%	$128.5013	$128.50	$128.50	$128.50
Purchase #3	$223.90	11.138%	$248.838	$248.84	$248.85	$248.80
Purchase #4	$16.64	7.509%	$17.8895	$17.89	$17.90	$17.90
Purchase #5	$246.45	11.514%	$274.8263	$274.83	$274.85	$274.80
Purchase #6	$238.50	10.594%	$263.7667	$263.77	$263.75	$263.80
Purchase #7	$17.70	13.688%	$20.1228	$20.12	$20.10	$20.10
7 purchase totals =	$1,005.18		$1,110.5917	$1,110.60	$1,110.60	$1,110.50