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	$133.55	7.380%	$143.406	$143.41	$143.40	$143.40
Purchase #2	$95.48	8.693%	$103.7801	$103.78	$103.80	$103.80
Purchase #3	$14.98	5.259%	$15.7678	$15.77	$15.75	$15.80
Purchase #4	$171.78	4.222%	$179.0326	$179.03	$179.05	$179.00
Purchase #5	$101.56	9.436%	$111.1432	$111.14	$111.15	$111.10
Purchase #6	$54.43	4.454%	$56.8543	$56.85	$56.85	$56.90
Purchase #7	$146.33	11.830%	$163.6408	$163.64	$163.65	$163.60
7 purchase totals =	$718.11		$773.6248	$773.62	$773.65	$773.60