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	$59.27	8.527%	$64.324	$64.32	$64.30	$64.30
Purchase #2	$30.97	11.675%	$34.5857	$34.59	$34.60	$34.60
Purchase #3	$158.41	12.578%	$178.3348	$178.33	$178.35	$178.30
Purchase #4	$47.27	4.713%	$49.4978	$49.50	$49.50	$49.50
Purchase #5	$211.39	11.598%	$235.907	$235.91	$235.90	$235.90
Purchase #6	$147.31	10.316%	$162.5065	$162.51	$162.50	$162.50
Purchase #7	$57.94	5.180%	$60.9413	$60.94	$60.95	$60.90
7 purchase totals =	$712.56		$786.0971	$786.10	$786.10	$786.00