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	$211.41	11.293%	$235.2845	$235.28	$235.30	$235.30
Purchase #2	$64.62	10.734%	$71.5563	$71.56	$71.55	$71.60
Purchase #3	$118.25	7.762%	$127.4286	$127.43	$127.45	$127.40
Purchase #4	$104.52	12.603%	$117.6927	$117.69	$117.70	$117.70
Purchase #5	$131.69	4.310%	$137.3658	$137.37	$137.35	$137.40
Purchase #6	$118.71	7.192%	$127.2476	$127.25	$127.25	$127.20
Purchase #7	$37.56	13.495%	$42.6287	$42.63	$42.65	$42.60
7 purchase totals =	$786.76		$859.2042	$859.21	$859.25	$859.20