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	$167.76	10.869%	$185.9938	$185.99	$186.00	$186.00
Purchase #2	$238.83	11.653%	$266.6609	$266.66	$266.65	$266.70
Purchase #3	$32.54	10.463%	$35.9447	$35.94	$35.95	$35.90
Purchase #4	$11.27	10.571%	$12.4614	$12.46	$12.45	$12.50
Purchase #5	$114.58	8.564%	$124.3926	$124.39	$124.40	$124.40
Purchase #6	$235.92	3.442%	$244.0404	$244.04	$244.05	$244.00
Purchase #7	$132.81	13.233%	$150.3847	$150.38	$150.40	$150.40
7 purchase totals =	$933.71		$1,019.8785	$1,019.86	$1,019.90	$1,019.90