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	$235.52	6.782%	$251.493	$251.49	$251.50	$251.50
Purchase #2	$208.47	4.227%	$217.282	$217.28	$217.30	$217.30
Purchase #3	$61.81	13.610%	$70.2223	$70.22	$70.20	$70.20
Purchase #4	$241.30	4.236%	$251.5215	$251.52	$251.50	$251.50
Purchase #5	$39.95	5.837%	$42.2819	$42.28	$42.30	$42.30
Purchase #6	$155.59	13.282%	$176.2555	$176.26	$176.25	$176.30
Purchase #7	$92.61	10.616%	$102.4415	$102.44	$102.45	$102.40
7 purchase totals =	$1,035.25		$1,111.4977	$1,111.49	$1,111.50	$1,111.50