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	$144.85	4.654%	$151.5913	$151.59	$151.60	$151.60
Purchase #2	$147.55	12.637%	$166.1959	$166.20	$166.20	$166.20
Purchase #3	$193.49	10.422%	$213.6555	$213.66	$213.65	$213.70
Purchase #4	$54.77	12.776%	$61.7674	$61.77	$61.75	$61.80
Purchase #5	$149.58	10.268%	$164.9389	$164.94	$164.95	$164.90
Purchase #6	$144.87	9.183%	$158.1734	$158.17	$158.15	$158.20
Purchase #7	$38.61	9.376%	$42.2301	$42.23	$42.25	$42.20
7 purchase totals =	$873.72		$958.5525	$958.56	$958.55	$958.60