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	$157.47	10.348%	$173.765	$173.77	$173.75	$173.80
Purchase #2	$183.76	8.223%	$198.8706	$198.87	$198.85	$198.90
Purchase #3	$119.44	3.438%	$123.5463	$123.55	$123.55	$123.50
Purchase #4	$50.81	9.853%	$55.8163	$55.82	$55.80	$55.80
Purchase #5	$105.61	9.716%	$115.8711	$115.87	$115.85	$115.90
Purchase #6	$36.94	7.103%	$39.5638	$39.56	$39.55	$39.60
Purchase #7	$104.29	6.758%	$111.3379	$111.34	$111.35	$111.30
7 purchase totals =	$758.32		$818.7710	$818.78	$818.70	$818.80