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	$101.79	9.178%	$111.1323	$111.13	$111.15	$111.10
Purchase #2	$144.60	9.187%	$157.8844	$157.88	$157.90	$157.90
Purchase #3	$97.47	9.609%	$106.8359	$106.84	$106.85	$106.80
Purchase #4	$55.68	4.604%	$58.2435	$58.24	$58.25	$58.20
Purchase #5	$80.61	11.482%	$89.8656	$89.87	$89.85	$89.90
Purchase #6	$121.78	3.705%	$126.2919	$126.29	$126.30	$126.30
Purchase #7	$34.86	10.130%	$38.3913	$38.39	$38.40	$38.40
7 purchase totals =	$636.79		$688.6449	$688.64	$688.70	$688.60