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	$85.90	11.286%	$95.5947	$95.59	$95.60	$95.60
Purchase #2	$153.28	13.729%	$174.3238	$174.32	$174.30	$174.30
Purchase #3	$164.62	10.255%	$181.5018	$181.50	$181.50	$181.50
Purchase #4	$154.42	7.625%	$166.1945	$166.19	$166.20	$166.20
Purchase #5	$231.30	10.141%	$254.7561	$254.76	$254.75	$254.80
Purchase #6	$210.81	9.371%	$230.565	$230.57	$230.55	$230.60
Purchase #7	$19.68	6.517%	$20.9625	$20.96	$20.95	$21.00
7 purchase totals =	$1,020.01		$1,123.8984	$1,123.89	$1,123.85	$1,124.00