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	$11.87	8.331%	$12.8589	$12.86	$12.85	$12.90
Purchase #2	$236.61	7.412%	$254.1475	$254.15	$254.15	$254.10
Purchase #3	$168.82	3.363%	$174.4974	$174.50	$174.50	$174.50
Purchase #4	$212.68	4.602%	$222.4675	$222.47	$222.45	$222.50
Purchase #5	$95.82	8.138%	$103.6178	$103.62	$103.60	$103.60
Purchase #6	$194.60	11.361%	$216.7085	$216.71	$216.70	$216.70
Purchase #7	$146.64	3.583%	$151.8941	$151.89	$151.90	$151.90
7 purchase totals =	$1,067.04		$1,136.1917	$1,136.20	$1,136.15	$1,136.20