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	$136.88	11.112%	$152.0901	$152.09	$152.10	$152.10
Purchase #2	$149.39	10.500%	$165.076	$165.08	$165.10	$165.10
Purchase #3	$41.52	12.402%	$46.6693	$46.67	$46.65	$46.70
Purchase #4	$240.30	10.642%	$265.8727	$265.87	$265.85	$265.90
Purchase #5	$12.40	8.553%	$13.4606	$13.46	$13.45	$13.50
Purchase #6	$145.55	13.856%	$165.7174	$165.72	$165.70	$165.70
Purchase #7	$122.65	13.335%	$139.0054	$139.01	$139.00	$139.00
7 purchase totals =	$848.69		$947.8915	$947.90	$947.85	$948.00