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	$39.80	9.358%	$43.5245	$43.52	$43.50	$43.50
Purchase #2	$205.83	5.317%	$216.774	$216.77	$216.75	$216.80
Purchase #3	$34.60	8.133%	$37.414	$37.41	$37.40	$37.40
Purchase #4	$49.29	6.592%	$52.5392	$52.54	$52.55	$52.50
Purchase #5	$209.75	3.793%	$217.7058	$217.71	$217.70	$217.70
Purchase #6	$248.25	5.326%	$261.4718	$261.47	$261.45	$261.50
Purchase #7	$115.51	9.848%	$126.8854	$126.89	$126.90	$126.90
7 purchase totals =	$903.03		$956.3147	$956.31	$956.25	$956.30