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	$166.38	11.267%	$185.126	$185.13	$185.15	$185.10
Purchase #2	$223.39	12.775%	$251.9281	$251.93	$251.95	$251.90
Purchase #3	$164.33	5.540%	$173.4339	$173.43	$173.45	$173.40
Purchase #4	$94.78	5.560%	$100.0498	$100.05	$100.05	$100.00
Purchase #5	$214.35	3.830%	$222.5596	$222.56	$222.55	$222.60
Purchase #6	$141.83	13.585%	$161.0976	$161.10	$161.10	$161.10
Purchase #7	$204.28	13.280%	$231.4084	$231.41	$231.40	$231.40
7 purchase totals =	$1,209.34		$1,325.6034	$1,325.61	$1,325.65	$1,325.50