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	$199.94	9.655%	$219.2442	$219.24	$219.25	$219.20
Purchase #2	$211.78	3.365%	$218.9064	$218.91	$218.90	$218.90
Purchase #3	$138.58	3.300%	$143.1531	$143.15	$143.15	$143.20
Purchase #4	$83.89	13.188%	$94.9534	$94.95	$94.95	$95.00
Purchase #5	$64.55	4.393%	$67.3857	$67.39	$67.40	$67.40
Purchase #6	$186.77	13.560%	$212.096	$212.10	$212.10	$212.10
Purchase #7	$54.78	12.493%	$61.6237	$61.62	$61.60	$61.60
7 purchase totals =	$940.29		$1,017.3625	$1,017.36	$1,017.35	$1,017.40