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	$115.42	10.327%	$127.3394	$127.34	$127.35	$127.30
Purchase #2	$86.80	3.604%	$89.9283	$89.93	$89.95	$89.90
Purchase #3	$113.81	11.504%	$126.9027	$126.90	$126.90	$126.90
Purchase #4	$207.70	6.523%	$221.2483	$221.25	$221.25	$221.20
Purchase #5	$205.26	13.566%	$233.1056	$233.11	$233.10	$233.10
Purchase #6	$127.53	3.524%	$132.0242	$132.02	$132.00	$132.00
Purchase #7	$95.86	13.601%	$108.8979	$108.90	$108.90	$108.90
7 purchase totals =	$952.38		$1,039.4464	$1,039.45	$1,039.45	$1,039.30