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	$116.59	8.826%	$126.8802	$126.88	$126.90	$126.90
Purchase #2	$107.77	3.635%	$111.6874	$111.69	$111.70	$111.70
Purchase #3	$204.65	5.696%	$216.3069	$216.31	$216.30	$216.30
Purchase #4	$210.25	4.532%	$219.7785	$219.78	$219.80	$219.80
Purchase #5	$191.43	8.169%	$207.0679	$207.07	$207.05	$207.10
Purchase #6	$41.69	4.557%	$43.5898	$43.59	$43.60	$43.60
Purchase #7	$156.94	10.687%	$173.7122	$173.71	$173.70	$173.70
7 purchase totals =	$1,029.32		$1,099.0229	$1,099.03	$1,099.05	$1,099.10