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	$112.65	13.256%	$127.5829	$127.58	$127.60	$127.60
Purchase #2	$225.99	3.211%	$233.2465	$233.25	$233.25	$233.20
Purchase #3	$53.65	4.529%	$56.0798	$56.08	$56.10	$56.10
Purchase #4	$154.54	12.307%	$173.5592	$173.56	$173.55	$173.60
Purchase #5	$102.30	12.783%	$115.377	$115.38	$115.40	$115.40
Purchase #6	$143.75	5.371%	$151.4708	$151.47	$151.45	$151.50
Purchase #7	$27.77	12.812%	$31.3279	$31.33	$31.35	$31.30
7 purchase totals =	$820.65		$888.6441	$888.65	$888.70	$888.70