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	$69.80	10.435%	$77.0836	$77.08	$77.10	$77.10
Purchase #2	$186.65	11.550%	$208.2081	$208.21	$208.20	$208.20
Purchase #3	$47.72	11.796%	$53.3491	$53.35	$53.35	$53.30
Purchase #4	$49.37	10.670%	$54.6378	$54.64	$54.65	$54.60
Purchase #5	$111.50	6.597%	$118.8557	$118.86	$118.85	$118.90
Purchase #6	$165.61	4.616%	$173.2546	$173.25	$173.25	$173.30
Purchase #7	$215.28	5.854%	$227.8825	$227.88	$227.90	$227.90
7 purchase totals =	$845.93		$913.2714	$913.27	$913.30	$913.30