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	$192.45	8.530%	$208.866	$208.87	$208.85	$208.90
Purchase #2	$248.79	13.666%	$282.7896	$282.79	$282.80	$282.80
Purchase #3	$111.33	4.605%	$116.4567	$116.46	$116.45	$116.50
Purchase #4	$196.92	3.671%	$204.1489	$204.15	$204.15	$204.10
Purchase #5	$145.86	11.641%	$162.8396	$162.84	$162.85	$162.80
Purchase #6	$152.95	12.495%	$172.0611	$172.06	$172.05	$172.10
Purchase #7	$134.62	11.695%	$150.3638	$150.36	$150.35	$150.40
7 purchase totals =	$1,182.92		$1,297.5257	$1,297.53	$1,297.50	$1,297.60