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	$205.83	4.852%	$215.8169	$215.82	$215.80	$215.80
Purchase #2	$80.58	11.343%	$89.7202	$89.72	$89.70	$89.70
Purchase #3	$112.69	3.135%	$116.2228	$116.22	$116.20	$116.20
Purchase #4	$225.34	7.103%	$241.3459	$241.35	$241.35	$241.30
Purchase #5	$226.70	12.683%	$255.4524	$255.45	$255.45	$255.50
Purchase #6	$250.54	10.693%	$277.3302	$277.33	$277.35	$277.30
Purchase #7	$131.88	5.615%	$139.2851	$139.29	$139.30	$139.30
7 purchase totals =	$1,233.56		$1,335.1735	$1,335.18	$1,335.15	$1,335.10