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	$102.29	3.235%	$105.5991	$105.60	$105.60	$105.60
Purchase #2	$87.61	6.591%	$93.3844	$93.38	$93.40	$93.40
Purchase #3	$197.87	12.195%	$222.0002	$222.00	$222.00	$222.00
Purchase #4	$109.27	8.731%	$118.8104	$118.81	$118.80	$118.80
Purchase #5	$116.82	6.565%	$124.4892	$124.49	$124.50	$124.50
Purchase #6	$249.37	4.508%	$260.6116	$260.61	$260.60	$260.60
Purchase #7	$152.33	6.759%	$162.626	$162.63	$162.65	$162.60
7 purchase totals =	$1,015.56		$1,087.5209	$1,087.52	$1,087.55	$1,087.50