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	$67.26	13.848%	$76.5742	$76.57	$76.55	$76.60
Purchase #2	$196.68	13.210%	$222.6614	$222.66	$222.65	$222.70
Purchase #3	$230.94	13.710%	$262.6019	$262.60	$262.60	$262.60
Purchase #4	$45.98	6.691%	$49.0565	$49.06	$49.05	$49.10
Purchase #5	$166.34	4.593%	$173.98	$173.98	$174.00	$174.00
Purchase #6	$104.78	7.684%	$112.8313	$112.83	$112.85	$112.80
Purchase #7	$42.85	10.389%	$47.3017	$47.30	$47.30	$47.30
7 purchase totals =	$854.83		$945.0070	$945.00	$945.00	$945.10