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	$216.82	4.696%	$227.0019	$227.00	$227.00	$227.00
Purchase #2	$122.54	6.736%	$130.7943	$130.79	$130.80	$130.80
Purchase #3	$30.97	3.230%	$31.9703	$31.97	$31.95	$32.00
Purchase #4	$28.52	12.499%	$32.0847	$32.08	$32.10	$32.10
Purchase #5	$105.60	5.398%	$111.3003	$111.30	$111.30	$111.30
Purchase #6	$100.68	3.677%	$104.382	$104.38	$104.40	$104.40
Purchase #7	$145.44	13.142%	$164.5537	$164.55	$164.55	$164.60
7 purchase totals =	$750.57		$802.0872	$802.07	$802.10	$802.20