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	$105.91	5.273%	$111.4946	$111.49	$111.50	$111.50
Purchase #2	$205.26	11.626%	$229.1235	$229.12	$229.10	$229.10
Purchase #3	$207.47	7.512%	$223.0551	$223.06	$223.05	$223.10
Purchase #4	$226.39	5.558%	$238.9728	$238.97	$238.95	$239.00
Purchase #5	$79.70	13.296%	$90.2969	$90.30	$90.30	$90.30
Purchase #6	$111.63	5.693%	$117.9851	$117.99	$118.00	$118.00
Purchase #7	$130.38	8.593%	$141.5836	$141.58	$141.60	$141.60
7 purchase totals =	$1,066.74		$1,152.5116	$1,152.51	$1,152.50	$1,152.60