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	$39.47	9.320%	$43.1486	$43.15	$43.15	$43.10
Purchase #2	$215.42	13.392%	$244.269	$244.27	$244.25	$244.30
Purchase #3	$37.59	10.254%	$41.4445	$41.44	$41.45	$41.40
Purchase #4	$72.41	7.396%	$77.7654	$77.77	$77.75	$77.80
Purchase #5	$155.38	6.719%	$165.82	$165.82	$165.80	$165.80
Purchase #6	$146.99	6.591%	$156.6781	$156.68	$156.70	$156.70
Purchase #7	$29.83	12.590%	$33.5856	$33.59	$33.60	$33.60
7 purchase totals =	$697.09		$762.7112	$762.72	$762.70	$762.70