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	$137.71	11.702%	$153.8248	$153.82	$153.80	$153.80
Purchase #2	$69.51	12.838%	$78.4337	$78.43	$78.45	$78.40
Purchase #3	$183.62	13.532%	$208.4675	$208.47	$208.45	$208.50
Purchase #4	$20.71	3.301%	$21.3936	$21.39	$21.40	$21.40
Purchase #5	$216.34	4.178%	$225.3787	$225.38	$225.40	$225.40
Purchase #6	$28.42	13.390%	$32.2254	$32.23	$32.25	$32.20
Purchase #7	$158.44	10.188%	$174.5819	$174.58	$174.60	$174.60
7 purchase totals =	$814.75		$894.3056	$894.30	$894.35	$894.30