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	$55.52	10.541%	$61.3724	$61.37	$61.35	$61.40
Purchase #2	$153.80	5.189%	$161.7807	$161.78	$161.80	$161.80
Purchase #3	$174.62	7.359%	$187.4703	$187.47	$187.45	$187.50
Purchase #4	$83.88	6.235%	$89.1099	$89.11	$89.10	$89.10
Purchase #5	$242.98	11.815%	$271.6881	$271.69	$271.70	$271.70
Purchase #6	$215.82	7.409%	$231.8101	$231.81	$231.80	$231.80
Purchase #7	$131.69	7.677%	$141.7998	$141.80	$141.80	$141.80
7 purchase totals =	$1,058.31		$1,145.0313	$1,145.03	$1,145.00	$1,145.10