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	$181.93	12.781%	$205.1825	$205.18	$205.20	$205.20
Purchase #2	$150.64	10.677%	$166.7238	$166.72	$166.70	$166.70
Purchase #3	$162.74	6.854%	$173.8942	$173.89	$173.90	$173.90
Purchase #4	$108.37	9.265%	$118.4105	$118.41	$118.40	$118.40
Purchase #5	$155.82	10.105%	$171.5656	$171.57	$171.55	$171.60
Purchase #6	$107.88	13.815%	$122.7836	$122.78	$122.80	$122.80
Purchase #7	$105.72	5.786%	$111.837	$111.84	$111.85	$111.80
7 purchase totals =	$973.10		$1,070.3972	$1,070.39	$1,070.40	$1,070.40