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	$187.93	13.131%	$212.6071	$212.61	$212.60	$212.60
Purchase #2	$111.57	13.348%	$126.4624	$126.46	$126.45	$126.50
Purchase #3	$19.50	5.156%	$20.5054	$20.51	$20.50	$20.50
Purchase #4	$47.71	10.232%	$52.5917	$52.59	$52.60	$52.60
Purchase #5	$239.78	5.628%	$253.2748	$253.27	$253.25	$253.30
Purchase #6	$107.63	11.225%	$119.7115	$119.71	$119.70	$119.70
Purchase #7	$132.73	5.146%	$139.5603	$139.56	$139.55	$139.60
7 purchase totals =	$846.85		$924.7132	$924.71	$924.65	$924.80