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	$178.28	10.193%	$196.4521	$196.45	$196.45	$196.50
Purchase #2	$126.26	10.706%	$139.7774	$139.78	$139.80	$139.80
Purchase #3	$41.74	4.527%	$43.6296	$43.63	$43.65	$43.60
Purchase #4	$99.63	11.601%	$111.1881	$111.19	$111.20	$111.20
Purchase #5	$56.77	13.294%	$64.317	$64.32	$64.30	$64.30
Purchase #6	$8.99	12.554%	$10.1186	$10.12	$10.10	$10.10
Purchase #7	$8.71	8.455%	$9.4464	$9.45	$9.45	$9.40
7 purchase totals =	$520.38		$574.9292	$574.94	$574.95	$574.90