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	$102.43	13.668%	$116.4301	$116.43	$116.45	$116.40
Purchase #2	$172.98	4.471%	$180.7139	$180.71	$180.70	$180.70
Purchase #3	$241.52	9.251%	$263.863	$263.86	$263.85	$263.90
Purchase #4	$84.54	6.746%	$90.2431	$90.24	$90.25	$90.20
Purchase #5	$142.28	5.547%	$150.1723	$150.17	$150.15	$150.20
Purchase #6	$49.33	7.742%	$53.1491	$53.15	$53.15	$53.10
Purchase #7	$173.53	11.854%	$194.1002	$194.10	$194.10	$194.10
7 purchase totals =	$966.61		$1,048.6717	$1,048.66	$1,048.65	$1,048.60