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	$159.70	10.242%	$176.0565	$176.06	$176.05	$176.10
Purchase #2	$57.93	9.862%	$63.6431	$63.64	$63.65	$63.60
Purchase #3	$76.92	7.620%	$82.7813	$82.78	$82.80	$82.80
Purchase #4	$188.59	12.151%	$211.5056	$211.51	$211.50	$211.50
Purchase #5	$96.52	5.207%	$101.5458	$101.55	$101.55	$101.50
Purchase #6	$18.77	13.539%	$21.3113	$21.31	$21.30	$21.30
Purchase #7	$96.61	3.673%	$100.1585	$100.16	$100.15	$100.20
7 purchase totals =	$695.04		$757.0021	$757.01	$757.00	$757.00