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	$167.78	3.577%	$173.7815	$173.78	$173.80	$173.80
Purchase #2	$131.79	5.800%	$139.4338	$139.43	$139.45	$139.40
Purchase #3	$108.87	7.247%	$116.7598	$116.76	$116.75	$116.80
Purchase #4	$123.52	8.724%	$134.2959	$134.30	$134.30	$134.30
Purchase #5	$215.73	3.649%	$223.602	$223.60	$223.60	$223.60
Purchase #6	$229.96	3.737%	$238.5536	$238.55	$238.55	$238.60
Purchase #7	$92.86	5.537%	$98.0017	$98.00	$98.00	$98.00
7 purchase totals =	$1,070.51		$1,124.4283	$1,124.42	$1,124.45	$1,124.50