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	$152.64	9.610%	$167.3087	$167.31	$167.30	$167.30
Purchase #2	$47.98	8.500%	$52.0583	$52.06	$52.05	$52.10
Purchase #3	$90.86	13.368%	$103.0062	$103.01	$103.00	$103.00
Purchase #4	$14.32	9.562%	$15.6893	$15.69	$15.70	$15.70
Purchase #5	$85.93	3.379%	$88.8336	$88.83	$88.85	$88.80
Purchase #6	$95.64	5.228%	$100.6401	$100.64	$100.65	$100.60
Purchase #7	$92.94	4.493%	$97.1158	$97.12	$97.10	$97.10
7 purchase totals =	$580.31		$624.6520	$624.66	$624.65	$624.60