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	$221.38	12.338%	$248.6939	$248.69	$248.70	$248.70
Purchase #2	$46.82	4.349%	$48.8562	$48.86	$48.85	$48.90
Purchase #3	$151.83	4.443%	$158.5758	$158.58	$158.60	$158.60
Purchase #4	$65.30	6.352%	$69.4479	$69.45	$69.45	$69.40
Purchase #5	$109.72	12.531%	$123.469	$123.47	$123.45	$123.50
Purchase #6	$248.96	5.874%	$263.5839	$263.58	$263.60	$263.60
Purchase #7	$230.39	12.839%	$259.9698	$259.97	$259.95	$260.00
7 purchase totals =	$1,074.40		$1,172.5965	$1,172.60	$1,172.60	$1,172.70