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	$150.92	3.779%	$156.6233	$156.62	$156.60	$156.60
Purchase #2	$162.40	11.496%	$181.0695	$181.07	$181.05	$181.10
Purchase #3	$83.88	12.554%	$94.4103	$94.41	$94.40	$94.40
Purchase #4	$52.63	4.215%	$54.8484	$54.85	$54.85	$54.80
Purchase #5	$166.85	5.607%	$176.2053	$176.21	$176.20	$176.20
Purchase #6	$109.99	12.570%	$123.8157	$123.82	$123.80	$123.80
Purchase #7	$158.60	13.688%	$180.3092	$180.31	$180.30	$180.30
7 purchase totals =	$885.27		$967.2817	$967.29	$967.20	$967.20