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	$96.64	13.125%	$109.324	$109.32	$109.30	$109.30
Purchase #2	$62.93	11.665%	$70.2708	$70.27	$70.25	$70.30
Purchase #3	$111.52	11.116%	$123.9166	$123.92	$123.90	$123.90
Purchase #4	$199.85	13.380%	$226.5899	$226.59	$226.60	$226.60
Purchase #5	$61.54	12.274%	$69.0934	$69.09	$69.10	$69.10
Purchase #6	$219.85	6.272%	$233.639	$233.64	$233.65	$233.60
Purchase #7	$116.50	9.598%	$127.6817	$127.68	$127.70	$127.70
7 purchase totals =	$868.83		$960.5154	$960.51	$960.50	$960.50