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	$184.90	6.814%	$197.4991	$197.50	$197.50	$197.50
Purchase #2	$11.58	4.116%	$12.0566	$12.06	$12.05	$12.10
Purchase #3	$123.59	3.564%	$127.9947	$127.99	$128.00	$128.00
Purchase #4	$119.75	6.411%	$127.4272	$127.43	$127.45	$127.40
Purchase #5	$117.84	11.501%	$131.3928	$131.39	$131.40	$131.40
Purchase #6	$39.57	7.279%	$42.4503	$42.45	$42.45	$42.50
Purchase #7	$149.52	5.846%	$158.2609	$158.26	$158.25	$158.30
7 purchase totals =	$746.75		$797.0816	$797.08	$797.10	$797.20