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	$50.28	6.452%	$53.5241	$53.52	$53.50	$53.50
Purchase #2	$57.79	11.500%	$64.4359	$64.44	$64.45	$64.40
Purchase #3	$18.55	4.603%	$19.4039	$19.40	$19.40	$19.40
Purchase #4	$118.66	4.372%	$123.8478	$123.85	$123.85	$123.80
Purchase #5	$240.92	6.393%	$256.322	$256.32	$256.30	$256.30
Purchase #6	$9.99	11.588%	$11.1476	$11.15	$11.15	$11.10
Purchase #7	$153.45	3.180%	$158.3297	$158.33	$158.35	$158.30
7 purchase totals =	$649.64		$687.0110	$687.01	$687.00	$686.80