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	$95.88	10.336%	$105.7902	$105.79	$105.80	$105.80
Purchase #2	$39.82	3.105%	$41.0564	$41.06	$41.05	$41.10
Purchase #3	$141.71	13.702%	$161.1271	$161.13	$161.15	$161.10
Purchase #4	$140.51	3.802%	$145.8522	$145.85	$145.85	$145.90
Purchase #5	$137.29	12.857%	$154.9414	$154.94	$154.95	$154.90
Purchase #6	$172.52	5.433%	$181.893	$181.89	$181.90	$181.90
Purchase #7	$145.31	4.407%	$151.7138	$151.71	$151.70	$151.70
7 purchase totals =	$873.04		$942.3741	$942.37	$942.40	$942.40