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	$44.31	5.156%	$46.5946	$46.59	$46.60	$46.60
Purchase #2	$136.48	13.248%	$154.5609	$154.56	$154.55	$154.60
Purchase #3	$45.35	9.120%	$49.4859	$49.49	$49.50	$49.50
Purchase #4	$68.73	5.854%	$72.7535	$72.75	$72.75	$72.80
Purchase #5	$38.45	7.838%	$41.4637	$41.46	$41.45	$41.50
Purchase #6	$222.65	4.723%	$233.1658	$233.17	$233.15	$233.20
Purchase #7	$177.25	6.801%	$189.3048	$189.30	$189.30	$189.30
7 purchase totals =	$733.22		$787.3292	$787.32	$787.30	$787.50