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	$183.48	3.583%	$190.0541	$190.05	$190.05	$190.10
Purchase #2	$226.29	6.537%	$241.0826	$241.08	$241.10	$241.10
Purchase #3	$119.52	10.283%	$131.8102	$131.81	$131.80	$131.80
Purchase #4	$74.73	10.526%	$82.5961	$82.60	$82.60	$82.60
Purchase #5	$160.44	6.234%	$170.4418	$170.44	$170.45	$170.40
Purchase #6	$125.26	13.714%	$142.4382	$142.44	$142.45	$142.40
Purchase #7	$80.78	12.227%	$90.657	$90.66	$90.65	$90.70
7 purchase totals =	$970.50		$1,049.0800	$1,049.08	$1,049.10	$1,049.10