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	$76.29	8.381%	$82.6839	$82.68	$82.70	$82.70
Purchase #2	$88.97	11.469%	$99.174	$99.17	$99.15	$99.20
Purchase #3	$153.65	8.745%	$167.0867	$167.09	$167.10	$167.10
Purchase #4	$46.28	10.852%	$51.3023	$51.30	$51.30	$51.30
Purchase #5	$26.37	13.224%	$29.8572	$29.86	$29.85	$29.90
Purchase #6	$39.53	12.635%	$44.5246	$44.52	$44.50	$44.50
Purchase #7	$73.90	6.133%	$78.4323	$78.43	$78.45	$78.40
7 purchase totals =	$504.99		$553.0610	$553.05	$553.05	$553.10