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	$143.45	9.257%	$156.7292	$156.73	$156.75	$156.70
Purchase #2	$49.43	10.169%	$54.4565	$54.46	$54.45	$54.50
Purchase #3	$147.60	3.838%	$153.2649	$153.26	$153.25	$153.30
Purchase #4	$111.36	11.302%	$123.9459	$123.95	$123.95	$123.90
Purchase #5	$192.92	9.409%	$211.0718	$211.07	$211.05	$211.10
Purchase #6	$144.94	9.592%	$158.8426	$158.84	$158.85	$158.80
Purchase #7	$68.64	5.838%	$72.6472	$72.65	$72.65	$72.60
7 purchase totals =	$858.34		$930.9581	$930.96	$930.95	$930.90