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	$237.49	10.497%	$262.4193	$262.42	$262.40	$262.40
Purchase #2	$148.76	12.467%	$167.3059	$167.31	$167.30	$167.30
Purchase #3	$49.76	7.724%	$53.6035	$53.60	$53.60	$53.60
Purchase #4	$26.52	4.208%	$27.636	$27.64	$27.65	$27.60
Purchase #5	$189.71	3.283%	$195.9382	$195.94	$195.95	$195.90
Purchase #6	$239.82	9.698%	$263.0777	$263.08	$263.10	$263.10
Purchase #7	$82.82	9.667%	$90.8262	$90.83	$90.85	$90.80
7 purchase totals =	$974.88		$1,060.8068	$1,060.82	$1,060.85	$1,060.70