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	$153.99	12.323%	$172.9662	$172.97	$172.95	$173.00
Purchase #2	$54.85	9.121%	$59.8529	$59.85	$59.85	$59.90
Purchase #3	$176.32	5.326%	$185.7108	$185.71	$185.70	$185.70
Purchase #4	$120.65	10.470%	$133.2821	$133.28	$133.30	$133.30
Purchase #5	$226.88	12.847%	$256.0273	$256.03	$256.05	$256.00
Purchase #6	$145.63	6.185%	$154.6372	$154.64	$154.65	$154.60
Purchase #7	$189.26	3.786%	$196.4254	$196.43	$196.45	$196.40
7 purchase totals =	$1,067.58		$1,158.9019	$1,158.91	$1,158.95	$1,158.90