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	$180.46	5.639%	$190.6361	$190.64	$190.65	$190.60
Purchase #2	$230.83	10.723%	$255.5819	$255.58	$255.60	$255.60
Purchase #3	$123.90	12.294%	$139.1323	$139.13	$139.15	$139.10
Purchase #4	$184.59	5.233%	$194.2496	$194.25	$194.25	$194.20
Purchase #5	$169.90	10.476%	$187.6987	$187.70	$187.70	$187.70
Purchase #6	$98.86	10.524%	$109.264	$109.26	$109.25	$109.30
Purchase #7	$10.60	6.431%	$11.2817	$11.28	$11.30	$11.30
7 purchase totals =	$999.14		$1,087.8443	$1,087.84	$1,087.90	$1,087.80