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	$119.46	10.149%	$131.584	$131.58	$131.60	$131.60
Purchase #2	$53.68	3.422%	$55.5169	$55.52	$55.50	$55.50
Purchase #3	$115.59	3.253%	$119.3501	$119.35	$119.35	$119.40
Purchase #4	$23.34	5.416%	$24.6041	$24.60	$24.60	$24.60
Purchase #5	$109.39	11.680%	$122.1668	$122.17	$122.15	$122.20
Purchase #6	$21.99	9.146%	$24.0012	$24.00	$24.00	$24.00
Purchase #7	$172.53	11.236%	$191.9155	$191.92	$191.90	$191.90
7 purchase totals =	$615.98		$669.1386	$669.14	$669.10	$669.20