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	$116.83	10.289%	$128.8506	$128.85	$128.85	$128.90
Purchase #2	$245.70	3.764%	$254.9481	$254.95	$254.95	$254.90
Purchase #3	$142.81	11.758%	$159.6016	$159.60	$159.60	$159.60
Purchase #4	$139.69	4.231%	$145.6003	$145.60	$145.60	$145.60
Purchase #5	$154.57	11.409%	$172.2049	$172.20	$172.20	$172.20
Purchase #6	$53.35	7.151%	$57.1651	$57.17	$57.15	$57.20
Purchase #7	$185.45	6.853%	$198.1589	$198.16	$198.15	$198.20
7 purchase totals =	$1,038.40		$1,116.5295	$1,116.53	$1,116.50	$1,116.60