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	$137.68	4.205%	$143.4694	$143.47	$143.45	$143.50
Purchase #2	$80.25	7.116%	$85.9606	$85.96	$85.95	$86.00
Purchase #3	$56.41	5.357%	$59.4319	$59.43	$59.45	$59.40
Purchase #4	$61.65	4.119%	$64.1894	$64.19	$64.20	$64.20
Purchase #5	$100.47	11.120%	$111.6423	$111.64	$111.65	$111.60
Purchase #6	$32.82	5.560%	$34.6448	$34.64	$34.65	$34.60
Purchase #7	$172.42	3.647%	$178.7082	$178.71	$178.70	$178.70
7 purchase totals =	$641.70		$678.0466	$678.04	$678.05	$678.00