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	$99.51	4.186%	$103.6755	$103.68	$103.70	$103.70
Purchase #2	$222.71	10.681%	$246.4977	$246.50	$246.50	$246.50
Purchase #3	$54.38	6.845%	$58.1023	$58.10	$58.10	$58.10
Purchase #4	$239.67	6.730%	$255.7998	$255.80	$255.80	$255.80
Purchase #5	$133.89	12.857%	$151.1042	$151.10	$151.10	$151.10
Purchase #6	$169.48	10.128%	$186.6449	$186.64	$186.65	$186.60
Purchase #7	$50.70	3.589%	$52.5196	$52.52	$52.50	$52.50
7 purchase totals =	$970.34		$1,054.3440	$1,054.34	$1,054.35	$1,054.30