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	$64.75	8.748%	$70.4143	$70.41	$70.40	$70.40
Purchase #2	$110.42	5.766%	$116.7868	$116.79	$116.80	$116.80
Purchase #3	$119.34	6.688%	$127.3215	$127.32	$127.30	$127.30
Purchase #4	$152.40	12.861%	$172.0002	$172.00	$172.00	$172.00
Purchase #5	$217.47	9.174%	$237.4207	$237.42	$237.40	$237.40
Purchase #6	$155.28	5.831%	$164.3344	$164.33	$164.35	$164.30
Purchase #7	$42.80	12.773%	$48.2668	$48.27	$48.25	$48.30
7 purchase totals =	$862.46		$936.5447	$936.54	$936.50	$936.50