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	$166.41	4.326%	$173.6089	$173.61	$173.60	$173.60
Purchase #2	$132.32	10.186%	$145.7981	$145.80	$145.80	$145.80
Purchase #3	$150.71	9.116%	$164.4487	$164.45	$164.45	$164.40
Purchase #4	$31.42	4.249%	$32.755	$32.76	$32.75	$32.80
Purchase #5	$232.32	3.114%	$239.5544	$239.55	$239.55	$239.60
Purchase #6	$33.95	9.749%	$37.2598	$37.26	$37.25	$37.30
Purchase #7	$215.89	9.785%	$237.0148	$237.01	$237.00	$237.00
7 purchase totals =	$963.02		$1,030.4397	$1,030.44	$1,030.40	$1,030.50