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	$98.62	13.454%	$111.8883	$111.89	$111.90	$111.90
Purchase #2	$160.74	3.745%	$166.7597	$166.76	$166.75	$166.80
Purchase #3	$142.26	13.450%	$161.394	$161.39	$161.40	$161.40
Purchase #4	$18.39	13.798%	$20.9275	$20.93	$20.95	$20.90
Purchase #5	$39.37	6.389%	$41.8853	$41.89	$41.90	$41.90
Purchase #6	$11.66	4.746%	$12.2134	$12.21	$12.20	$12.20
Purchase #7	$45.99	13.825%	$52.3481	$52.35	$52.35	$52.30
7 purchase totals =	$517.03		$567.4163	$567.42	$567.45	$567.40