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	$241.61	10.327%	$266.5611	$266.56	$266.55	$266.60
Purchase #2	$76.37	8.337%	$82.737	$82.74	$82.75	$82.70
Purchase #3	$71.36	10.627%	$78.9434	$78.94	$78.95	$78.90
Purchase #4	$172.60	3.758%	$179.0863	$179.09	$179.10	$179.10
Purchase #5	$148.40	3.531%	$153.64	$153.64	$153.65	$153.60
Purchase #6	$49.38	11.407%	$55.0128	$55.01	$55.00	$55.00
Purchase #7	$57.45	12.497%	$64.6295	$64.63	$64.65	$64.60
7 purchase totals =	$817.17		$880.6101	$880.61	$880.65	$880.50