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	$161.73	6.772%	$172.6824	$172.68	$172.70	$172.70
Purchase #2	$120.78	11.606%	$134.7977	$134.80	$134.80	$134.80
Purchase #3	$17.62	3.636%	$18.2607	$18.26	$18.25	$18.30
Purchase #4	$11.32	11.376%	$12.6078	$12.61	$12.60	$12.60
Purchase #5	$65.31	3.540%	$67.622	$67.62	$67.60	$67.60
Purchase #6	$85.49	12.385%	$96.0779	$96.08	$96.10	$96.10
Purchase #7	$121.48	4.667%	$127.1495	$127.15	$127.15	$127.10
7 purchase totals =	$583.73		$629.1980	$629.20	$629.20	$629.20