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	$93.95	5.164%	$98.8016	$98.80	$98.80	$98.80
Purchase #2	$230.32	10.792%	$255.1761	$255.18	$255.20	$255.20
Purchase #3	$85.49	5.734%	$90.392	$90.39	$90.40	$90.40
Purchase #4	$118.48	13.607%	$134.6016	$134.60	$134.60	$134.60
Purchase #5	$182.58	3.356%	$188.7074	$188.71	$188.70	$188.70
Purchase #6	$205.26	12.594%	$231.1104	$231.11	$231.10	$231.10
Purchase #7	$237.75	10.724%	$263.2463	$263.25	$263.25	$263.20
7 purchase totals =	$1,153.83		$1,262.0354	$1,262.04	$1,262.05	$1,262.00