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	$245.30	5.642%	$259.1398	$259.14	$259.15	$259.10
Purchase #2	$155.88	12.110%	$174.7571	$174.76	$174.75	$174.80
Purchase #3	$173.72	10.493%	$191.9484	$191.95	$191.95	$191.90
Purchase #4	$132.60	7.580%	$142.6511	$142.65	$142.65	$142.70
Purchase #5	$213.32	4.105%	$222.0768	$222.08	$222.10	$222.10
Purchase #6	$71.46	11.358%	$79.5764	$79.58	$79.60	$79.60
Purchase #7	$68.83	5.750%	$72.7877	$72.79	$72.80	$72.80
7 purchase totals =	$1,061.11		$1,142.9373	$1,142.95	$1,143.00	$1,143.00