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	$72.77	7.249%	$78.0451	$78.05	$78.05	$78.00
Purchase #2	$188.44	6.647%	$200.9656	$200.97	$200.95	$201.00
Purchase #3	$101.59	12.677%	$114.4686	$114.47	$114.45	$114.50
Purchase #4	$230.45	8.664%	$250.4162	$250.42	$250.40	$250.40
Purchase #5	$11.29	13.804%	$12.8485	$12.85	$12.85	$12.80
Purchase #6	$107.47	10.461%	$118.7124	$118.71	$118.70	$118.70
Purchase #7	$20.44	9.862%	$22.4558	$22.46	$22.45	$22.50
7 purchase totals =	$732.45		$797.9122	$797.93	$797.85	$797.90