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	$200.78	12.257%	$225.3896	$225.39	$225.40	$225.40
Purchase #2	$144.42	6.355%	$153.5979	$153.60	$153.60	$153.60
Purchase #3	$99.35	10.238%	$109.5215	$109.52	$109.50	$109.50
Purchase #4	$162.94	13.178%	$184.4122	$184.41	$184.40	$184.40
Purchase #5	$126.47	4.383%	$132.0132	$132.01	$132.00	$132.00
Purchase #6	$92.33	13.735%	$105.0115	$105.01	$105.00	$105.00
Purchase #7	$122.47	11.106%	$136.0715	$136.07	$136.05	$136.10
7 purchase totals =	$948.76		$1,046.0174	$1,046.01	$1,045.95	$1,046.00