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	$49.84	11.551%	$55.597	$55.60	$55.60	$55.60
Purchase #2	$216.55	10.842%	$240.0284	$240.03	$240.05	$240.00
Purchase #3	$151.67	3.595%	$157.1225	$157.12	$157.10	$157.10
Purchase #4	$110.69	9.209%	$120.8834	$120.88	$120.90	$120.90
Purchase #5	$230.61	8.525%	$250.2695	$250.27	$250.25	$250.30
Purchase #6	$117.38	8.719%	$127.6144	$127.61	$127.60	$127.60
Purchase #7	$112.67	5.111%	$118.4286	$118.43	$118.45	$118.40
7 purchase totals =	$989.41		$1,069.9438	$1,069.94	$1,069.95	$1,069.90