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	$53.55	10.698%	$59.2788	$59.28	$59.30	$59.30
Purchase #2	$121.88	7.607%	$131.1514	$131.15	$131.15	$131.20
Purchase #3	$164.45	12.871%	$185.6164	$185.62	$185.60	$185.60
Purchase #4	$136.49	13.844%	$155.3857	$155.39	$155.40	$155.40
Purchase #5	$218.57	3.874%	$227.0374	$227.04	$227.05	$227.00
Purchase #6	$177.50	5.596%	$187.4329	$187.43	$187.45	$187.40
Purchase #7	$173.74	6.344%	$184.7621	$184.76	$184.75	$184.80
7 purchase totals =	$1,046.18		$1,130.6647	$1,130.67	$1,130.70	$1,130.70