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	$168.62	5.580%	$178.029	$178.03	$178.05	$178.00
Purchase #2	$18.70	13.520%	$21.2282	$21.23	$21.25	$21.20
Purchase #3	$132.43	7.665%	$142.5808	$142.58	$142.60	$142.60
Purchase #4	$177.97	10.331%	$196.3561	$196.36	$196.35	$196.40
Purchase #5	$180.76	4.505%	$188.9032	$188.90	$188.90	$188.90
Purchase #6	$182.64	4.206%	$190.3218	$190.32	$190.30	$190.30
Purchase #7	$48.37	13.675%	$54.9846	$54.98	$55.00	$55.00
7 purchase totals =	$909.49		$972.4037	$972.40	$972.45	$972.40