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	$103.63	7.488%	$111.3898	$111.39	$111.40	$111.40
Purchase #2	$241.73	9.813%	$265.451	$265.45	$265.45	$265.50
Purchase #3	$195.99	3.606%	$203.0574	$203.06	$203.05	$203.10
Purchase #4	$54.71	9.612%	$59.9687	$59.97	$59.95	$60.00
Purchase #5	$244.47	5.785%	$258.6126	$258.61	$258.60	$258.60
Purchase #6	$37.88	5.404%	$39.927	$39.93	$39.95	$39.90
Purchase #7	$122.56	4.267%	$127.7896	$127.79	$127.80	$127.80
7 purchase totals =	$1,000.97		$1,066.1961	$1,066.20	$1,066.20	$1,066.30