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	$49.25	13.450%	$55.8741	$55.87	$55.85	$55.90
Purchase #2	$147.81	3.848%	$153.4977	$153.50	$153.50	$153.50
Purchase #3	$50.46	6.414%	$53.6965	$53.70	$53.70	$53.70
Purchase #4	$95.93	8.203%	$103.7991	$103.80	$103.80	$103.80
Purchase #5	$65.75	10.652%	$72.7537	$72.75	$72.75	$72.80
Purchase #6	$91.99	9.115%	$100.3749	$100.37	$100.35	$100.40
Purchase #7	$56.75	9.791%	$62.3064	$62.31	$62.30	$62.30
7 purchase totals =	$557.94		$602.3024	$602.30	$602.25	$602.40