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	$151.46	13.793%	$172.3509	$172.35	$172.35	$172.40
Purchase #2	$177.93	9.326%	$194.5238	$194.52	$194.50	$194.50
Purchase #3	$45.67	6.674%	$48.718	$48.72	$48.70	$48.70
Purchase #4	$241.87	10.237%	$266.6302	$266.63	$266.65	$266.60
Purchase #5	$112.53	13.227%	$127.4143	$127.41	$127.40	$127.40
Purchase #6	$87.59	5.203%	$92.1473	$92.15	$92.15	$92.10
Purchase #7	$48.87	9.729%	$53.6246	$53.62	$53.60	$53.60
7 purchase totals =	$865.92		$955.4091	$955.40	$955.35	$955.30