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	$210.30	13.365%	$238.4066	$238.41	$238.40	$238.40
Purchase #2	$185.31	11.536%	$206.6874	$206.69	$206.70	$206.70
Purchase #3	$149.77	5.612%	$158.1751	$158.18	$158.20	$158.20
Purchase #4	$119.62	7.710%	$128.8427	$128.84	$128.85	$128.80
Purchase #5	$73.92	3.707%	$76.6602	$76.66	$76.65	$76.70
Purchase #6	$105.40	6.192%	$111.9264	$111.93	$111.95	$111.90
Purchase #7	$188.97	11.292%	$210.3085	$210.31	$210.30	$210.30
7 purchase totals =	$1,033.29		$1,131.0069	$1,131.02	$1,131.05	$1,131.00