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	$89.44	6.847%	$95.564	$95.56	$95.55	$95.60
Purchase #2	$91.78	6.339%	$97.5979	$97.60	$97.60	$97.60
Purchase #3	$87.52	3.753%	$90.8046	$90.80	$90.80	$90.80
Purchase #4	$82.69	7.615%	$88.9868	$88.99	$89.00	$89.00
Purchase #5	$145.40	13.162%	$164.5375	$164.54	$164.55	$164.50
Purchase #6	$230.52	10.867%	$255.5706	$255.57	$255.55	$255.60
Purchase #7	$207.86	8.510%	$225.5489	$225.55	$225.55	$225.50
7 purchase totals =	$935.21		$1,018.6103	$1,018.61	$1,018.60	$1,018.60