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	$26.51	8.498%	$28.7628	$28.76	$28.75	$28.80
Purchase #2	$193.29	6.281%	$205.4305	$205.43	$205.45	$205.40
Purchase #3	$37.32	5.722%	$39.4555	$39.46	$39.45	$39.50
Purchase #4	$46.27	9.231%	$50.5412	$50.54	$50.55	$50.50
Purchase #5	$225.76	13.149%	$255.4452	$255.45	$255.45	$255.40
Purchase #6	$222.92	3.424%	$230.5528	$230.55	$230.55	$230.60
Purchase #7	$235.77	5.725%	$249.2678	$249.27	$249.25	$249.30
7 purchase totals =	$987.84		$1,059.4558	$1,059.46	$1,059.45	$1,059.50