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	$215.92	4.490%	$225.6148	$225.61	$225.60	$225.60
Purchase #2	$200.93	12.874%	$226.7977	$226.80	$226.80	$226.80
Purchase #3	$139.59	5.824%	$147.7197	$147.72	$147.70	$147.70
Purchase #4	$142.89	6.186%	$151.7292	$151.73	$151.75	$151.70
Purchase #5	$106.80	4.420%	$111.5206	$111.52	$111.50	$111.50
Purchase #6	$43.32	7.138%	$46.4122	$46.41	$46.40	$46.40
Purchase #7	$154.54	13.761%	$175.8062	$175.81	$175.80	$175.80
7 purchase totals =	$1,003.99		$1,085.6004	$1,085.60	$1,085.55	$1,085.50