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	$31.31	9.613%	$34.3198	$34.32	$34.30	$34.30
Purchase #2	$18.26	8.588%	$19.8282	$19.83	$19.85	$19.80
Purchase #3	$39.66	10.826%	$43.9536	$43.95	$43.95	$44.00
Purchase #4	$75.37	9.199%	$82.3033	$82.30	$82.30	$82.30
Purchase #5	$115.34	10.486%	$127.4346	$127.43	$127.45	$127.40
Purchase #6	$172.30	10.396%	$190.2123	$190.21	$190.20	$190.20
Purchase #7	$56.98	10.386%	$62.8979	$62.90	$62.90	$62.90
7 purchase totals =	$509.22		$560.9497	$560.94	$560.95	$560.90