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	$121.97	4.143%	$127.0232	$127.02	$127.00	$127.00
Purchase #2	$53.28	4.684%	$55.7756	$55.78	$55.80	$55.80
Purchase #3	$56.50	7.233%	$60.5866	$60.59	$60.60	$60.60
Purchase #4	$62.79	12.136%	$70.4102	$70.41	$70.40	$70.40
Purchase #5	$74.34	10.384%	$82.0595	$82.06	$82.05	$82.10
Purchase #6	$9.73	10.726%	$10.7736	$10.77	$10.75	$10.80
Purchase #7	$164.41	6.318%	$174.7974	$174.80	$174.80	$174.80
7 purchase totals =	$543.02		$581.4261	$581.43	$581.40	$581.50