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	$64.26	13.464%	$72.912	$72.91	$72.90	$72.90
Purchase #2	$242.71	5.318%	$255.6173	$255.62	$255.60	$255.60
Purchase #3	$143.70	10.148%	$158.2827	$158.28	$158.30	$158.30
Purchase #4	$212.59	3.358%	$219.7288	$219.73	$219.75	$219.70
Purchase #5	$103.67	8.455%	$112.4353	$112.44	$112.45	$112.40
Purchase #6	$212.46	13.442%	$241.0189	$241.02	$241.00	$241.00
Purchase #7	$99.73	12.732%	$112.4276	$112.43	$112.45	$112.40
7 purchase totals =	$1,079.12		$1,172.4226	$1,172.43	$1,172.45	$1,172.30