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	$213.51	6.525%	$227.4415	$227.44	$227.45	$227.40
Purchase #2	$89.32	11.223%	$99.3444	$99.34	$99.35	$99.30
Purchase #3	$173.86	13.258%	$196.9104	$196.91	$196.90	$196.90
Purchase #4	$134.30	8.626%	$145.8847	$145.88	$145.90	$145.90
Purchase #5	$24.55	12.845%	$27.7034	$27.70	$27.70	$27.70
Purchase #6	$45.65	12.126%	$51.1855	$51.19	$51.20	$51.20
Purchase #7	$49.85	5.807%	$52.7448	$52.74	$52.75	$52.70
7 purchase totals =	$731.04		$801.2147	$801.20	$801.25	$801.10