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	$150.45	4.505%	$157.2278	$157.23	$157.25	$157.20
Purchase #2	$138.51	5.118%	$145.5989	$145.60	$145.60	$145.60
Purchase #3	$75.82	8.315%	$82.1244	$82.12	$82.10	$82.10
Purchase #4	$63.84	13.611%	$72.5293	$72.53	$72.55	$72.50
Purchase #5	$107.94	7.536%	$116.0744	$116.07	$116.05	$116.10
Purchase #6	$179.49	4.506%	$187.5778	$187.58	$187.60	$187.60
Purchase #7	$227.83	7.197%	$244.2269	$244.23	$244.25	$244.20
7 purchase totals =	$943.88		$1,005.3595	$1,005.36	$1,005.40	$1,005.30