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	$207.25	10.389%	$228.7812	$228.78	$228.80	$228.80
Purchase #2	$51.49	3.653%	$53.3709	$53.37	$53.35	$53.40
Purchase #3	$38.39	11.390%	$42.7626	$42.76	$42.75	$42.80
Purchase #4	$152.37	4.127%	$158.6583	$158.66	$158.65	$158.70
Purchase #5	$50.68	3.506%	$52.4568	$52.46	$52.45	$52.50
Purchase #6	$15.73	6.612%	$16.7701	$16.77	$16.75	$16.80
Purchase #7	$130.85	7.842%	$141.1113	$141.11	$141.10	$141.10
7 purchase totals =	$646.76		$693.9112	$693.91	$693.85	$694.10