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	$52.59	4.613%	$55.016	$55.02	$55.00	$55.00
Purchase #2	$40.75	5.232%	$42.882	$42.88	$42.90	$42.90
Purchase #3	$130.84	10.697%	$144.836	$144.84	$144.85	$144.80
Purchase #4	$13.90	4.612%	$14.5411	$14.54	$14.55	$14.50
Purchase #5	$131.68	6.446%	$140.1681	$140.17	$140.15	$140.20
Purchase #6	$158.70	9.267%	$173.4067	$173.41	$173.40	$173.40
Purchase #7	$158.75	5.475%	$167.4416	$167.44	$167.45	$167.40
7 purchase totals =	$687.21		$738.2915	$738.30	$738.30	$738.20