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	$205.88	3.854%	$213.8146	$213.81	$213.80	$213.80
Purchase #2	$230.96	8.860%	$251.4231	$251.42	$251.40	$251.40
Purchase #3	$60.48	11.749%	$67.5858	$67.59	$67.60	$67.60
Purchase #4	$239.42	13.436%	$271.5885	$271.59	$271.60	$271.60
Purchase #5	$131.72	9.792%	$144.618	$144.62	$144.60	$144.60
Purchase #6	$130.83	10.784%	$144.9387	$144.94	$144.95	$144.90
Purchase #7	$52.67	10.443%	$58.1703	$58.17	$58.15	$58.20
7 purchase totals =	$1,051.96		$1,152.1390	$1,152.14	$1,152.10	$1,152.10