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	$165.85	4.702%	$173.6483	$173.65	$173.65	$173.60
Purchase #2	$18.89	7.242%	$20.258	$20.26	$20.25	$20.30
Purchase #3	$17.38	12.205%	$19.5012	$19.50	$19.50	$19.50
Purchase #4	$175.51	13.719%	$199.5882	$199.59	$199.60	$199.60
Purchase #5	$143.85	3.127%	$148.3482	$148.35	$148.35	$148.30
Purchase #6	$211.85	5.196%	$222.8577	$222.86	$222.85	$222.90
Purchase #7	$57.37	3.699%	$59.4921	$59.49	$59.50	$59.50
7 purchase totals =	$790.70		$843.6937	$843.70	$843.70	$843.70