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	$13.52	5.353%	$14.2437	$14.24	$14.25	$14.20
Purchase #2	$108.78	4.636%	$113.823	$113.82	$113.80	$113.80
Purchase #3	$38.27	12.734%	$43.1433	$43.14	$43.15	$43.10
Purchase #4	$142.60	8.251%	$154.3659	$154.37	$154.35	$154.40
Purchase #5	$246.68	8.278%	$267.1002	$267.10	$267.10	$267.10
Purchase #6	$65.29	11.630%	$72.8832	$72.88	$72.90	$72.90
Purchase #7	$111.33	11.103%	$123.691	$123.69	$123.70	$123.70
7 purchase totals =	$726.47		$789.2503	$789.24	$789.25	$789.20