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	$81.42	10.350%	$89.847	$89.85	$89.85	$89.80
Purchase #2	$10.62	5.381%	$11.1915	$11.19	$11.20	$11.20
Purchase #3	$153.70	11.406%	$171.231	$171.23	$171.25	$171.20
Purchase #4	$33.32	5.647%	$35.2016	$35.20	$35.20	$35.20
Purchase #5	$70.67	10.636%	$78.1865	$78.19	$78.20	$78.20
Purchase #6	$34.31	3.831%	$35.6244	$35.62	$35.60	$35.60
Purchase #7	$183.65	9.396%	$200.9058	$200.91	$200.90	$200.90
7 purchase totals =	$567.69		$622.1878	$622.19	$622.20	$622.10