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	$200.41	11.398%	$223.2527	$223.25	$223.25	$223.30
Purchase #2	$186.60	10.125%	$205.4933	$205.49	$205.50	$205.50
Purchase #3	$166.57	3.408%	$172.2467	$172.25	$172.25	$172.20
Purchase #4	$161.95	8.119%	$175.0987	$175.10	$175.10	$175.10
Purchase #5	$64.27	13.667%	$73.0538	$73.05	$73.05	$73.10
Purchase #6	$45.94	7.307%	$49.2968	$49.30	$49.30	$49.30
Purchase #7	$57.65	7.245%	$61.8267	$61.83	$61.85	$61.80
7 purchase totals =	$883.39		$960.2687	$960.27	$960.30	$960.30