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	$128.65	13.357%	$145.8338	$145.83	$145.85	$145.80
Purchase #2	$148.25	11.748%	$165.6664	$165.67	$165.65	$165.70
Purchase #3	$193.60	11.557%	$215.9744	$215.97	$215.95	$216.00
Purchase #4	$166.52	12.681%	$187.6364	$187.64	$187.65	$187.60
Purchase #5	$239.75	11.147%	$266.4749	$266.47	$266.45	$266.50
Purchase #6	$152.78	9.812%	$167.7708	$167.77	$167.75	$167.80
Purchase #7	$48.97	4.806%	$51.3235	$51.32	$51.30	$51.30
7 purchase totals =	$1,078.52		$1,200.6802	$1,200.67	$1,200.60	$1,200.70