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	$118.60	13.213%	$134.2706	$134.27	$134.25	$134.30
Purchase #2	$85.41	7.775%	$92.0506	$92.05	$92.05	$92.10
Purchase #3	$38.55	9.750%	$42.3086	$42.31	$42.30	$42.30
Purchase #4	$226.46	3.299%	$233.9309	$233.93	$233.95	$233.90
Purchase #5	$85.43	5.509%	$90.1363	$90.14	$90.15	$90.10
Purchase #6	$235.47	11.690%	$262.9964	$263.00	$263.00	$263.00
Purchase #7	$153.47	6.775%	$163.8676	$163.87	$163.85	$163.90
7 purchase totals =	$943.39		$1,019.5610	$1,019.57	$1,019.55	$1,019.60