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	$243.60	11.725%	$272.1621	$272.16	$272.15	$272.20
Purchase #2	$169.37	3.591%	$175.4521	$175.45	$175.45	$175.50
Purchase #3	$81.42	9.324%	$89.0116	$89.01	$89.00	$89.00
Purchase #4	$40.79	3.491%	$42.214	$42.21	$42.20	$42.20
Purchase #5	$234.72	10.312%	$258.9243	$258.92	$258.90	$258.90
Purchase #6	$158.37	7.240%	$169.836	$169.84	$169.85	$169.80
Purchase #7	$239.26	6.758%	$255.4292	$255.43	$255.45	$255.40
7 purchase totals =	$1,167.53		$1,263.0293	$1,263.02	$1,263.00	$1,263.00