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	$40.47	4.164%	$42.1552	$42.16	$42.15	$42.20
Purchase #2	$95.83	12.342%	$107.6573	$107.66	$107.65	$107.70
Purchase #3	$177.42	9.388%	$194.0762	$194.08	$194.10	$194.10
Purchase #4	$250.75	10.499%	$277.0762	$277.08	$277.10	$277.10
Purchase #5	$185.58	10.616%	$205.2812	$205.28	$205.30	$205.30
Purchase #6	$114.39	13.750%	$130.1186	$130.12	$130.10	$130.10
Purchase #7	$160.81	6.684%	$171.5585	$171.56	$171.55	$171.60
7 purchase totals =	$1,025.25		$1,127.9232	$1,127.94	$1,127.95	$1,128.10