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	$174.85	12.398%	$196.5279	$196.53	$196.55	$196.50
Purchase #2	$227.91	10.252%	$251.2753	$251.28	$251.30	$251.30
Purchase #3	$215.47	8.626%	$234.0564	$234.06	$234.05	$234.10
Purchase #4	$228.94	4.242%	$238.6516	$238.65	$238.65	$238.70
Purchase #5	$226.86	12.649%	$255.5555	$255.56	$255.55	$255.60
Purchase #6	$162.62	6.593%	$173.3415	$173.34	$173.35	$173.30
Purchase #7	$19.53	3.593%	$20.2317	$20.23	$20.25	$20.20
7 purchase totals =	$1,256.18		$1,369.6399	$1,369.65	$1,369.70	$1,369.70