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	$151.38	4.678%	$158.4616	$158.46	$158.45	$158.50
Purchase #2	$230.50	9.832%	$253.1628	$253.16	$253.15	$253.20
Purchase #3	$190.72	4.774%	$199.825	$199.83	$199.85	$199.80
Purchase #4	$211.95	8.846%	$230.6991	$230.70	$230.70	$230.70
Purchase #5	$43.61	11.744%	$48.7316	$48.73	$48.75	$48.70
Purchase #6	$121.47	9.396%	$132.8833	$132.88	$132.90	$132.90
Purchase #7	$69.36	4.697%	$72.6178	$72.62	$72.60	$72.60
7 purchase totals =	$1,018.99		$1,096.3812	$1,096.38	$1,096.40	$1,096.40