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	$111.77	10.753%	$123.7886	$123.79	$123.80	$123.80
Purchase #2	$211.39	12.410%	$237.6235	$237.62	$237.60	$237.60
Purchase #3	$32.32	13.406%	$36.6528	$36.65	$36.65	$36.70
Purchase #4	$159.52	8.523%	$173.1159	$173.12	$173.10	$173.10
Purchase #5	$56.30	10.427%	$62.1704	$62.17	$62.15	$62.20
Purchase #6	$169.76	7.128%	$181.8605	$181.86	$181.85	$181.90
Purchase #7	$221.51	3.510%	$229.285	$229.29	$229.30	$229.30
7 purchase totals =	$962.57		$1,044.4967	$1,044.50	$1,044.45	$1,044.60