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	$123.36	7.501%	$132.6132	$132.61	$132.60	$132.60
Purchase #2	$45.31	11.855%	$50.6815	$50.68	$50.70	$50.70
Purchase #3	$55.91	11.574%	$62.381	$62.38	$62.40	$62.40
Purchase #4	$35.27	11.147%	$39.2015	$39.20	$39.20	$39.20
Purchase #5	$64.88	11.195%	$72.1433	$72.14	$72.15	$72.10
Purchase #6	$94.97	12.326%	$106.676	$106.68	$106.70	$106.70
Purchase #7	$38.82	3.845%	$40.3126	$40.31	$40.30	$40.30
7 purchase totals =	$458.52		$504.0091	$504.00	$504.05	$504.00