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	$112.35	13.230%	$127.2139	$127.21	$127.20	$127.20
Purchase #2	$66.63	5.742%	$70.4559	$70.46	$70.45	$70.50
Purchase #3	$70.75	13.867%	$80.5609	$80.56	$80.55	$80.60
Purchase #4	$41.44	5.154%	$43.5758	$43.58	$43.60	$43.60
Purchase #5	$218.62	9.221%	$238.779	$238.78	$238.80	$238.80
Purchase #6	$110.43	3.479%	$114.2719	$114.27	$114.25	$114.30
Purchase #7	$74.68	3.305%	$77.1482	$77.15	$77.15	$77.10
7 purchase totals =	$694.90		$752.0056	$752.01	$752.00	$752.10