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	$120.83	11.414%	$134.6215	$134.62	$134.60	$134.60
Purchase #2	$34.69	6.592%	$36.9768	$36.98	$37.00	$37.00
Purchase #3	$108.76	6.681%	$116.0263	$116.03	$116.05	$116.00
Purchase #4	$208.52	8.591%	$226.434	$226.43	$226.45	$226.40
Purchase #5	$81.35	9.769%	$89.2971	$89.30	$89.30	$89.30
Purchase #6	$161.88	5.870%	$171.3824	$171.38	$171.40	$171.40
Purchase #7	$243.42	5.141%	$255.9342	$255.93	$255.95	$255.90
7 purchase totals =	$959.45		$1,030.6723	$1,030.67	$1,030.75	$1,030.60