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	$153.50	3.254%	$158.4949	$158.49	$158.50	$158.50
Purchase #2	$127.56	7.404%	$137.0045	$137.00	$137.00	$137.00
Purchase #3	$195.83	10.202%	$215.8086	$215.81	$215.80	$215.80
Purchase #4	$114.50	4.102%	$119.1968	$119.20	$119.20	$119.20
Purchase #5	$235.99	7.740%	$254.2556	$254.26	$254.25	$254.30
Purchase #6	$129.52	6.119%	$137.4453	$137.45	$137.45	$137.40
Purchase #7	$63.82	11.393%	$71.091	$71.09	$71.10	$71.10
7 purchase totals =	$1,020.72		$1,093.2967	$1,093.30	$1,093.30	$1,093.30