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	$54.96	7.248%	$58.9435	$58.94	$58.95	$58.90
Purchase #2	$229.45	8.165%	$248.1846	$248.18	$248.20	$248.20
Purchase #3	$48.65	3.530%	$50.3673	$50.37	$50.35	$50.40
Purchase #4	$38.85	3.477%	$40.2008	$40.20	$40.20	$40.20
Purchase #5	$48.35	10.141%	$53.2532	$53.25	$53.25	$53.30
Purchase #6	$51.47	12.582%	$57.946	$57.95	$57.95	$57.90
Purchase #7	$101.60	10.180%	$111.9429	$111.94	$111.95	$111.90
7 purchase totals =	$573.33		$620.8383	$620.83	$620.85	$620.80