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	$179.72	10.860%	$199.2376	$199.24	$199.25	$199.20
Purchase #2	$242.80	5.274%	$255.6053	$255.61	$255.60	$255.60
Purchase #3	$10.67	7.564%	$11.4771	$11.48	$11.50	$11.50
Purchase #4	$122.45	13.146%	$138.5473	$138.55	$138.55	$138.50
Purchase #5	$192.93	9.421%	$211.1059	$211.11	$211.10	$211.10
Purchase #6	$9.89	10.350%	$10.9136	$10.91	$10.90	$10.90
Purchase #7	$106.30	5.106%	$111.7277	$111.73	$111.75	$111.70
7 purchase totals =	$864.76		$938.6145	$938.63	$938.65	$938.50