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	$15.88	8.745%	$17.2687	$17.27	$17.25	$17.30
Purchase #2	$218.91	8.736%	$238.034	$238.03	$238.05	$238.00
Purchase #3	$243.75	4.750%	$255.3281	$255.33	$255.35	$255.30
Purchase #4	$31.84	10.337%	$35.1313	$35.13	$35.15	$35.10
Purchase #5	$77.27	4.385%	$80.6583	$80.66	$80.65	$80.70
Purchase #6	$60.37	8.642%	$65.5872	$65.59	$65.60	$65.60
Purchase #7	$231.52	13.364%	$262.4603	$262.46	$262.45	$262.50
7 purchase totals =	$879.54		$954.4679	$954.47	$954.50	$954.50