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	$11.83	12.142%	$13.2664	$13.27	$13.25	$13.30
Purchase #2	$50.86	5.420%	$53.6166	$53.62	$53.60	$53.60
Purchase #3	$137.69	7.651%	$148.2247	$148.22	$148.20	$148.20
Purchase #4	$128.86	3.671%	$133.5905	$133.59	$133.60	$133.60
Purchase #5	$218.30	7.124%	$233.8517	$233.85	$233.85	$233.90
Purchase #6	$193.97	6.163%	$205.9244	$205.92	$205.90	$205.90
Purchase #7	$228.78	13.105%	$258.7616	$258.76	$258.75	$258.80
7 purchase totals =	$970.29		$1,047.2359	$1,047.23	$1,047.15	$1,047.30