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	$183.60	11.829%	$205.318	$205.32	$205.30	$205.30
Purchase #2	$72.95	13.845%	$83.0499	$83.05	$83.05	$83.00
Purchase #3	$170.77	10.676%	$189.0014	$189.00	$189.00	$189.00
Purchase #4	$127.54	8.274%	$138.0927	$138.09	$138.10	$138.10
Purchase #5	$67.37	7.505%	$72.4261	$72.43	$72.45	$72.40
Purchase #6	$11.27	12.781%	$12.7104	$12.71	$12.70	$12.70
Purchase #7	$117.57	11.853%	$131.5056	$131.51	$131.50	$131.50
7 purchase totals =	$751.07		$832.1041	$832.11	$832.10	$832.00