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	$14.37	6.649%	$15.3255	$15.33	$15.35	$15.30
Purchase #2	$10.79	7.335%	$11.5814	$11.58	$11.60	$11.60
Purchase #3	$160.75	11.735%	$179.614	$179.61	$179.60	$179.60
Purchase #4	$118.84	7.681%	$127.9681	$127.97	$127.95	$128.00
Purchase #5	$105.42	6.420%	$112.188	$112.19	$112.20	$112.20
Purchase #6	$78.37	3.384%	$81.022	$81.02	$81.00	$81.00
Purchase #7	$124.32	3.152%	$128.2386	$128.24	$128.25	$128.20
7 purchase totals =	$612.86		$655.9376	$655.94	$655.95	$655.90