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	$159.62	5.325%	$168.1198	$168.12	$168.10	$168.10
Purchase #2	$222.70	8.389%	$241.3823	$241.38	$241.40	$241.40
Purchase #3	$247.94	3.472%	$256.5485	$256.55	$256.55	$256.50
Purchase #4	$62.92	9.501%	$68.898	$68.90	$68.90	$68.90
Purchase #5	$123.85	7.326%	$132.9233	$132.92	$132.90	$132.90
Purchase #6	$154.84	10.640%	$171.315	$171.32	$171.30	$171.30
Purchase #7	$83.84	7.233%	$89.9041	$89.90	$89.90	$89.90
7 purchase totals =	$1,055.71		$1,129.0910	$1,129.09	$1,129.05	$1,129.00