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	$154.58	5.373%	$162.8856	$162.89	$162.90	$162.90
Purchase #2	$144.28	9.752%	$158.3502	$158.35	$158.35	$158.40
Purchase #3	$188.50	6.509%	$200.7695	$200.77	$200.75	$200.80
Purchase #4	$188.97	13.747%	$214.9477	$214.95	$214.95	$214.90
Purchase #5	$82.93	11.555%	$92.5126	$92.51	$92.50	$92.50
Purchase #6	$45.40	7.167%	$48.6538	$48.65	$48.65	$48.70
Purchase #7	$186.65	7.559%	$200.7589	$200.76	$200.75	$200.80
7 purchase totals =	$991.31		$1,078.8783	$1,078.88	$1,078.85	$1,079.00