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	$143.29	7.699%	$154.3219	$154.32	$154.30	$154.30
Purchase #2	$119.78	10.300%	$132.1173	$132.12	$132.10	$132.10
Purchase #3	$162.32	7.494%	$174.4843	$174.48	$174.50	$174.50
Purchase #4	$131.94	7.245%	$141.4991	$141.50	$141.50	$141.50
Purchase #5	$19.64	13.727%	$22.336	$22.34	$22.35	$22.30
Purchase #6	$151.90	5.742%	$160.6221	$160.62	$160.60	$160.60
Purchase #7	$19.50	11.225%	$21.6889	$21.69	$21.70	$21.70
7 purchase totals =	$748.37		$807.0696	$807.07	$807.05	$807.00