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	$139.61	9.845%	$153.3546	$153.35	$153.35	$153.40
Purchase #2	$216.52	10.190%	$238.5834	$238.58	$238.60	$238.60
Purchase #3	$85.86	4.858%	$90.0311	$90.03	$90.05	$90.00
Purchase #4	$177.65	10.807%	$196.8486	$196.85	$196.85	$196.80
Purchase #5	$68.25	7.560%	$73.4097	$73.41	$73.40	$73.40
Purchase #6	$139.94	4.440%	$146.1533	$146.15	$146.15	$146.20
Purchase #7	$238.75	6.129%	$253.383	$253.38	$253.40	$253.40
7 purchase totals =	$1,066.58		$1,151.7637	$1,151.75	$1,151.80	$1,151.80