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	$118.87	12.537%	$133.7727	$133.77	$133.75	$133.80
Purchase #2	$156.31	10.113%	$172.1176	$172.12	$172.10	$172.10
Purchase #3	$49.72	12.525%	$55.9474	$55.95	$55.95	$55.90
Purchase #4	$248.44	9.210%	$271.3213	$271.32	$271.30	$271.30
Purchase #5	$98.47	6.811%	$105.1768	$105.18	$105.20	$105.20
Purchase #6	$147.77	12.366%	$166.0432	$166.04	$166.05	$166.00
Purchase #7	$58.92	5.609%	$62.2248	$62.22	$62.20	$62.20
7 purchase totals =	$878.50		$966.6038	$966.60	$966.55	$966.50