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	$208.61	12.455%	$234.5924	$234.59	$234.60	$234.60
Purchase #2	$188.69	4.359%	$196.915	$196.92	$196.90	$196.90
Purchase #3	$199.93	3.772%	$207.4714	$207.47	$207.45	$207.50
Purchase #4	$112.55	13.477%	$127.7184	$127.72	$127.70	$127.70
Purchase #5	$43.83	10.202%	$48.3015	$48.30	$48.30	$48.30
Purchase #6	$177.96	9.676%	$195.1794	$195.18	$195.20	$195.20
Purchase #7	$116.33	9.255%	$127.0963	$127.10	$127.10	$127.10
7 purchase totals =	$1,047.90		$1,137.2744	$1,137.28	$1,137.25	$1,137.30