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	$168.29	9.563%	$184.3836	$184.38	$184.40	$184.40
Purchase #2	$52.84	12.255%	$59.3155	$59.32	$59.30	$59.30
Purchase #3	$179.77	8.122%	$194.3709	$194.37	$194.35	$194.40
Purchase #4	$168.60	12.855%	$190.2735	$190.27	$190.25	$190.30
Purchase #5	$49.91	9.467%	$54.635	$54.64	$54.65	$54.60
Purchase #6	$229.79	12.479%	$258.4655	$258.47	$258.45	$258.50
Purchase #7	$143.84	4.233%	$149.9287	$149.93	$149.95	$149.90
7 purchase totals =	$993.04		$1,091.3727	$1,091.38	$1,091.35	$1,091.40