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	$241.42	7.848%	$260.3666	$260.37	$260.35	$260.40
Purchase #2	$40.83	13.661%	$46.4078	$46.41	$46.40	$46.40
Purchase #3	$27.89	10.397%	$30.7897	$30.79	$30.80	$30.80
Purchase #4	$83.92	9.426%	$91.8303	$91.83	$91.85	$91.80
Purchase #5	$45.26	6.123%	$48.0313	$48.03	$48.05	$48.00
Purchase #6	$111.72	7.665%	$120.2833	$120.28	$120.30	$120.30
Purchase #7	$187.77	4.651%	$196.5032	$196.50	$196.50	$196.50
7 purchase totals =	$738.81		$794.2122	$794.21	$794.25	$794.20