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	$32.85	6.226%	$34.8952	$34.90	$34.90	$34.90
Purchase #2	$84.70	5.632%	$89.4703	$89.47	$89.45	$89.50
Purchase #3	$61.89	5.255%	$65.1423	$65.14	$65.15	$65.10
Purchase #4	$32.93	10.300%	$36.3218	$36.32	$36.30	$36.30
Purchase #5	$148.44	12.278%	$166.6655	$166.67	$166.65	$166.70
Purchase #6	$87.80	3.621%	$90.9792	$90.98	$91.00	$91.00
Purchase #7	$9.28	3.270%	$9.5835	$9.58	$9.60	$9.60
7 purchase totals =	$457.89		$493.0578	$493.06	$493.05	$493.10