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	$63.45	5.374%	$66.8598	$66.86	$66.85	$66.90
Purchase #2	$145.33	6.682%	$155.041	$155.04	$155.05	$155.00
Purchase #3	$181.81	9.359%	$198.8256	$198.83	$198.85	$198.80
Purchase #4	$88.79	9.153%	$96.9169	$96.92	$96.90	$96.90
Purchase #5	$48.58	12.866%	$54.8303	$54.83	$54.85	$54.80
Purchase #6	$168.38	8.363%	$182.4616	$182.46	$182.45	$182.50
Purchase #7	$40.92	12.348%	$45.9728	$45.97	$45.95	$46.00
7 purchase totals =	$737.26		$800.9080	$800.91	$800.90	$800.90