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	$46.92	12.646%	$52.8535	$52.85	$52.85	$52.90
Purchase #2	$95.83	9.712%	$105.137	$105.14	$105.15	$105.10
Purchase #3	$33.35	4.778%	$34.9435	$34.94	$34.95	$34.90
Purchase #4	$233.31	11.333%	$259.751	$259.75	$259.75	$259.80
Purchase #5	$67.59	12.242%	$75.8644	$75.86	$75.85	$75.90
Purchase #6	$137.30	12.259%	$154.1316	$154.13	$154.15	$154.10
Purchase #7	$47.72	5.406%	$50.2997	$50.30	$50.30	$50.30
7 purchase totals =	$662.02		$732.9807	$732.97	$733.00	$733.00