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	$76.93	12.269%	$86.3685	$86.37	$86.35	$86.40
Purchase #2	$49.77	5.860%	$52.6865	$52.69	$52.70	$52.70
Purchase #3	$49.65	13.824%	$56.5136	$56.51	$56.50	$56.50
Purchase #4	$138.38	12.379%	$155.5101	$155.51	$155.50	$155.50
Purchase #5	$85.45	6.243%	$90.7846	$90.78	$90.80	$90.80
Purchase #6	$50.49	7.114%	$54.0819	$54.08	$54.10	$54.10
Purchase #7	$115.49	10.227%	$127.3012	$127.30	$127.30	$127.30
7 purchase totals =	$566.16		$623.2464	$623.24	$623.25	$623.30