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	$60.61	11.291%	$67.4535	$67.45	$67.45	$67.50
Purchase #2	$29.49	11.506%	$32.8831	$32.88	$32.90	$32.90
Purchase #3	$198.27	11.400%	$220.8728	$220.87	$220.85	$220.90
Purchase #4	$5.56	11.196%	$6.1825	$6.18	$6.20	$6.20
Purchase #5	$29.50	10.365%	$32.5577	$32.56	$32.55	$32.60
Purchase #6	$71.46	8.593%	$77.6006	$77.60	$77.60	$77.60
Purchase #7	$238.88	5.230%	$251.3734	$251.37	$251.35	$251.40
7 purchase totals =	$633.77		$688.9236	$688.91	$688.90	$689.10