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	$89.42	5.183%	$94.0546	$94.05	$94.05	$94.10
Purchase #2	$199.49	12.146%	$223.7201	$223.72	$223.70	$223.70
Purchase #3	$43.73	13.379%	$49.5806	$49.58	$49.60	$49.60
Purchase #4	$68.59	11.670%	$76.5945	$76.59	$76.60	$76.60
Purchase #5	$224.66	4.217%	$234.1339	$234.13	$234.15	$234.10
Purchase #6	$111.41	6.206%	$118.3241	$118.32	$118.30	$118.30
Purchase #7	$83.25	7.178%	$89.2257	$89.23	$89.25	$89.20
7 purchase totals =	$820.55		$885.6335	$885.62	$885.65	$885.60