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	$223.31	7.763%	$240.6456	$240.65	$240.65	$240.60
Purchase #2	$148.84	8.475%	$161.4542	$161.45	$161.45	$161.50
Purchase #3	$232.82	10.359%	$256.9378	$256.94	$256.95	$256.90
Purchase #4	$11.35	13.609%	$12.8946	$12.89	$12.90	$12.90
Purchase #5	$88.45	9.195%	$96.583	$96.58	$96.60	$96.60
Purchase #6	$238.30	10.237%	$262.6948	$262.69	$262.70	$262.70
Purchase #7	$49.71	10.370%	$54.8649	$54.86	$54.85	$54.90
7 purchase totals =	$992.78		$1,086.0749	$1,086.06	$1,086.10	$1,086.10