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	$46.97	8.201%	$50.822	$50.82	$50.80	$50.80
Purchase #2	$65.83	9.596%	$72.147	$72.15	$72.15	$72.10
Purchase #3	$224.76	13.658%	$255.4577	$255.46	$255.45	$255.50
Purchase #4	$123.27	10.271%	$135.9311	$135.93	$135.95	$135.90
Purchase #5	$194.69	13.506%	$220.9848	$220.98	$221.00	$221.00
Purchase #6	$87.83	4.509%	$91.7903	$91.79	$91.80	$91.80
Purchase #7	$146.69	8.792%	$159.587	$159.59	$159.60	$159.60
7 purchase totals =	$890.04		$986.7199	$986.72	$986.75	$986.70