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	$64.76	4.642%	$67.7662	$67.77	$67.75	$67.80
Purchase #2	$181.85	7.791%	$196.0179	$196.02	$196.00	$196.00
Purchase #3	$71.72	8.681%	$77.946	$77.95	$77.95	$77.90
Purchase #4	$59.75	9.161%	$65.2237	$65.22	$65.20	$65.20
Purchase #5	$185.58	5.643%	$196.0523	$196.05	$196.05	$196.10
Purchase #6	$207.27	12.551%	$233.2845	$233.28	$233.30	$233.30
Purchase #7	$75.42	5.687%	$79.7091	$79.71	$79.70	$79.70
7 purchase totals =	$846.35		$915.9997	$916.00	$915.95	$916.00