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	$116.83	9.481%	$127.9067	$127.91	$127.90	$127.90
Purchase #2	$138.32	9.545%	$151.5226	$151.52	$151.50	$151.50
Purchase #3	$16.37	8.611%	$17.7796	$17.78	$17.80	$17.80
Purchase #4	$242.81	5.464%	$256.0771	$256.08	$256.10	$256.10
Purchase #5	$96.61	9.187%	$105.4856	$105.49	$105.50	$105.50
Purchase #6	$72.51	13.191%	$82.0748	$82.07	$82.05	$82.10
Purchase #7	$211.68	6.549%	$225.5429	$225.54	$225.55	$225.50
7 purchase totals =	$895.13		$966.3893	$966.39	$966.40	$966.40