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	$217.43	12.439%	$244.4761	$244.48	$244.50	$244.50
Purchase #2	$220.83	9.551%	$241.9215	$241.92	$241.90	$241.90
Purchase #3	$177.92	3.447%	$184.0529	$184.05	$184.05	$184.10
Purchase #4	$196.73	9.687%	$215.7872	$215.79	$215.80	$215.80
Purchase #5	$123.37	7.532%	$132.6622	$132.66	$132.65	$132.70
Purchase #6	$42.51	3.185%	$43.8639	$43.86	$43.85	$43.90
Purchase #7	$33.64	13.771%	$38.2726	$38.27	$38.25	$38.30
7 purchase totals =	$1,012.43		$1,101.0364	$1,101.03	$1,101.00	$1,101.20