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	$224.63	10.607%	$248.4565	$248.46	$248.45	$248.50
Purchase #2	$6.84	5.672%	$7.228	$7.23	$7.25	$7.20
Purchase #3	$224.81	7.103%	$240.7783	$240.78	$240.80	$240.80
Purchase #4	$40.63	8.605%	$44.1262	$44.13	$44.15	$44.10
Purchase #5	$77.53	5.806%	$82.0314	$82.03	$82.05	$82.00
Purchase #6	$248.38	5.414%	$261.8273	$261.83	$261.85	$261.80
Purchase #7	$145.25	13.641%	$165.0636	$165.06	$165.05	$165.10
7 purchase totals =	$968.07		$1,049.5113	$1,049.52	$1,049.60	$1,049.50