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	$60.60	7.274%	$65.008	$65.01	$65.00	$65.00
Purchase #2	$95.87	12.609%	$107.9582	$107.96	$107.95	$108.00
Purchase #3	$98.75	6.187%	$104.8597	$104.86	$104.85	$104.90
Purchase #4	$133.46	11.338%	$148.5917	$148.59	$148.60	$148.60
Purchase #5	$27.68	4.244%	$28.8547	$28.85	$28.85	$28.90
Purchase #6	$36.85	5.653%	$38.9331	$38.93	$38.95	$38.90
Purchase #7	$63.99	13.322%	$72.5147	$72.51	$72.50	$72.50
7 purchase totals =	$517.20		$566.7201	$566.71	$566.70	$566.80