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	$120.29	9.466%	$131.6767	$131.68	$131.70	$131.70
Purchase #2	$22.70	9.117%	$24.7696	$24.77	$24.75	$24.80
Purchase #3	$89.63	13.756%	$101.9595	$101.96	$101.95	$102.00
Purchase #4	$44.54	6.868%	$47.599	$47.60	$47.60	$47.60
Purchase #5	$50.80	10.346%	$56.0558	$56.06	$56.05	$56.10
Purchase #6	$104.95	6.647%	$111.926	$111.93	$111.95	$111.90
Purchase #7	$29.33	11.727%	$32.7695	$32.77	$32.75	$32.80
7 purchase totals =	$462.24		$506.7561	$506.77	$506.75	$506.90