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	$105.52	10.653%	$116.761	$116.76	$116.75	$116.80
Purchase #2	$107.35	3.493%	$111.0997	$111.10	$111.10	$111.10
Purchase #3	$73.47	13.300%	$83.2415	$83.24	$83.25	$83.20
Purchase #4	$244.95	3.206%	$252.8031	$252.80	$252.80	$252.80
Purchase #5	$32.49	12.295%	$36.4846	$36.48	$36.50	$36.50
Purchase #6	$183.47	13.690%	$208.587	$208.59	$208.60	$208.60
Purchase #7	$61.31	7.568%	$65.9499	$65.95	$65.95	$65.90
7 purchase totals =	$808.56		$874.9268	$874.92	$874.95	$874.90