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	$205.77	9.742%	$225.8161	$225.82	$225.80	$225.80
Purchase #2	$159.55	4.267%	$166.358	$166.36	$166.35	$166.40
Purchase #3	$112.84	3.521%	$116.8131	$116.81	$116.80	$116.80
Purchase #4	$106.35	13.406%	$120.6073	$120.61	$120.60	$120.60
Purchase #5	$48.31	3.391%	$49.9482	$49.95	$49.95	$49.90
Purchase #6	$53.83	11.350%	$59.9397	$59.94	$59.95	$59.90
Purchase #7	$117.42	9.445%	$128.5103	$128.51	$128.50	$128.50
7 purchase totals =	$804.07		$867.9927	$868.00	$867.95	$867.90