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	$144.46	5.822%	$152.8705	$152.87	$152.85	$152.90
Purchase #2	$100.89	8.656%	$109.623	$109.62	$109.60	$109.60
Purchase #3	$173.77	9.606%	$190.4623	$190.46	$190.45	$190.50
Purchase #4	$21.75	13.170%	$24.6145	$24.61	$24.60	$24.60
Purchase #5	$97.35	10.273%	$107.3508	$107.35	$107.35	$107.40
Purchase #6	$229.79	4.640%	$240.4523	$240.45	$240.45	$240.50
Purchase #7	$106.28	9.451%	$116.3245	$116.32	$116.30	$116.30
7 purchase totals =	$874.29		$941.6979	$941.68	$941.60	$941.80