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	$87.38	3.867%	$90.759	$90.76	$90.75	$90.80
Purchase #2	$240.64	11.241%	$267.6903	$267.69	$267.70	$267.70
Purchase #3	$164.93	5.420%	$173.8692	$173.87	$173.85	$173.90
Purchase #4	$204.52	7.244%	$219.3354	$219.34	$219.35	$219.30
Purchase #5	$31.32	4.236%	$32.6467	$32.65	$32.65	$32.60
Purchase #6	$120.45	10.107%	$132.6239	$132.62	$132.60	$132.60
Purchase #7	$111.57	6.776%	$119.13	$119.13	$119.15	$119.10
7 purchase totals =	$960.81		$1,036.0545	$1,036.06	$1,036.05	$1,036.00