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	$222.66	3.332%	$230.079	$230.08	$230.10	$230.10
Purchase #2	$38.99	7.768%	$42.0187	$42.02	$42.00	$42.00
Purchase #3	$53.85	9.637%	$59.0395	$59.04	$59.05	$59.00
Purchase #4	$10.75	7.318%	$11.5367	$11.54	$11.55	$11.50
Purchase #5	$179.91	11.296%	$200.2326	$200.23	$200.25	$200.20
Purchase #6	$117.75	12.238%	$132.1602	$132.16	$132.15	$132.20
Purchase #7	$43.85	8.203%	$47.447	$47.45	$47.45	$47.40
7 purchase totals =	$667.76		$722.5137	$722.52	$722.55	$722.40