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	$163.35	6.440%	$173.8697	$173.87	$173.85	$173.90
Purchase #2	$59.32	12.141%	$66.522	$66.52	$66.50	$66.50
Purchase #3	$168.69	9.110%	$184.0577	$184.06	$184.05	$184.10
Purchase #4	$142.93	7.749%	$154.0056	$154.01	$154.00	$154.00
Purchase #5	$100.57	10.380%	$111.0092	$111.01	$111.00	$111.00
Purchase #6	$230.52	6.440%	$245.3655	$245.37	$245.35	$245.40
Purchase #7	$160.39	13.410%	$181.8983	$181.90	$181.90	$181.90
7 purchase totals =	$1,025.77		$1,116.7280	$1,116.74	$1,116.65	$1,116.80