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	$152.75	12.568%	$171.9476	$171.95	$171.95	$171.90
Purchase #2	$244.83	12.437%	$275.2795	$275.28	$275.30	$275.30
Purchase #3	$136.71	6.508%	$145.6071	$145.61	$145.60	$145.60
Purchase #4	$132.78	9.333%	$145.1724	$145.17	$145.15	$145.20
Purchase #5	$67.28	7.779%	$72.5137	$72.51	$72.50	$72.50
Purchase #6	$141.45	12.307%	$158.8583	$158.86	$158.85	$158.90
Purchase #7	$157.49	5.654%	$166.3945	$166.39	$166.40	$166.40
7 purchase totals =	$1,033.29		$1,135.7731	$1,135.77	$1,135.75	$1,135.80