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	$85.75	4.206%	$89.3566	$89.36	$89.35	$89.40
Purchase #2	$114.55	11.390%	$127.5972	$127.60	$127.60	$127.60
Purchase #3	$118.76	11.689%	$132.6419	$132.64	$132.65	$132.60
Purchase #4	$196.70	13.872%	$223.9862	$223.99	$224.00	$224.00
Purchase #5	$44.78	3.777%	$46.4713	$46.47	$46.45	$46.50
Purchase #6	$35.51	8.579%	$38.5564	$38.56	$38.55	$38.60
Purchase #7	$45.38	3.133%	$46.8018	$46.80	$46.80	$46.80
7 purchase totals =	$641.43		$705.4114	$705.42	$705.40	$705.50