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	$48.28	11.370%	$53.7694	$53.77	$53.75	$53.80
Purchase #2	$177.90	4.645%	$186.1635	$186.16	$186.15	$186.20
Purchase #3	$12.50	7.222%	$13.4028	$13.40	$13.40	$13.40
Purchase #4	$104.83	6.675%	$111.8274	$111.83	$111.85	$111.80
Purchase #5	$214.41	5.521%	$226.2476	$226.25	$226.25	$226.20
Purchase #6	$167.38	12.136%	$187.6932	$187.69	$187.70	$187.70
Purchase #7	$213.35	11.837%	$238.6042	$238.60	$238.60	$238.60
7 purchase totals =	$938.65		$1,017.7081	$1,017.70	$1,017.70	$1,017.70