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	$205.54	8.749%	$223.5227	$223.52	$223.50	$223.50
Purchase #2	$111.86	10.467%	$123.5684	$123.57	$123.55	$123.60
Purchase #3	$214.34	10.620%	$237.1029	$237.10	$237.10	$237.10
Purchase #4	$237.27	10.119%	$261.2794	$261.28	$261.30	$261.30
Purchase #5	$146.56	5.349%	$154.3995	$154.40	$154.40	$154.40
Purchase #6	$58.87	12.320%	$66.1228	$66.12	$66.10	$66.10
Purchase #7	$70.32	8.631%	$76.3893	$76.39	$76.40	$76.40
7 purchase totals =	$1,044.76		$1,142.3850	$1,142.38	$1,142.35	$1,142.40