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	$230.72	3.345%	$238.4376	$238.44	$238.45	$238.40
Purchase #2	$166.84	3.667%	$172.958	$172.96	$172.95	$173.00
Purchase #3	$35.88	7.210%	$38.4669	$38.47	$38.45	$38.50
Purchase #4	$94.39	5.783%	$99.8486	$99.85	$99.85	$99.80
Purchase #5	$204.75	4.675%	$214.3221	$214.32	$214.30	$214.30
Purchase #6	$60.47	8.258%	$65.4636	$65.46	$65.45	$65.50
Purchase #7	$21.68	10.144%	$23.8792	$23.88	$23.90	$23.90
7 purchase totals =	$814.73		$853.3760	$853.38	$853.35	$853.40