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	$49.94	10.777%	$55.322	$55.32	$55.30	$55.30
Purchase #2	$22.59	12.753%	$25.4709	$25.47	$25.45	$25.50
Purchase #3	$149.35	5.307%	$157.276	$157.28	$157.30	$157.30
Purchase #4	$35.82	6.492%	$38.1454	$38.15	$38.15	$38.10
Purchase #5	$187.80	4.684%	$196.5966	$196.60	$196.60	$196.60
Purchase #6	$40.57	8.192%	$43.8935	$43.89	$43.90	$43.90
Purchase #7	$35.43	6.858%	$37.8598	$37.86	$37.85	$37.90
7 purchase totals =	$521.50		$554.5642	$554.57	$554.55	$554.60