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	$175.89	3.742%	$182.4718	$182.47	$182.45	$182.50
Purchase #2	$111.79	13.246%	$126.5977	$126.60	$126.60	$126.60
Purchase #3	$207.82	3.751%	$215.6153	$215.62	$215.60	$215.60
Purchase #4	$153.94	12.272%	$172.8315	$172.83	$172.85	$172.80
Purchase #5	$43.52	5.466%	$45.8988	$45.90	$45.90	$45.90
Purchase #6	$224.69	9.450%	$245.9232	$245.92	$245.90	$245.90
Purchase #7	$135.37	7.219%	$145.1424	$145.14	$145.15	$145.10
7 purchase totals =	$1,053.02		$1,134.4807	$1,134.48	$1,134.45	$1,134.40