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	$128.61	4.664%	$134.6084	$134.61	$134.60	$134.60
Purchase #2	$105.70	5.510%	$111.5241	$111.52	$111.50	$111.50
Purchase #3	$94.78	6.250%	$100.7038	$100.70	$100.70	$100.70
Purchase #4	$175.62	6.660%	$187.3163	$187.32	$187.30	$187.30
Purchase #5	$202.89	6.193%	$215.455	$215.46	$215.45	$215.50
Purchase #6	$62.33	3.589%	$64.567	$64.57	$64.55	$64.60
Purchase #7	$28.50	13.282%	$32.2854	$32.29	$32.30	$32.30
7 purchase totals =	$798.43		$846.4600	$846.47	$846.40	$846.50