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	$24.44	8.412%	$26.4959	$26.50	$26.50	$26.50
Purchase #2	$111.31	10.141%	$122.5979	$122.60	$122.60	$122.60
Purchase #3	$157.78	7.221%	$169.1733	$169.17	$169.15	$169.20
Purchase #4	$153.82	5.595%	$162.4262	$162.43	$162.45	$162.40
Purchase #5	$85.62	4.108%	$89.1373	$89.14	$89.15	$89.10
Purchase #6	$181.39	4.119%	$188.8615	$188.86	$188.85	$188.90
Purchase #7	$229.45	12.822%	$258.8701	$258.87	$258.85	$258.90
7 purchase totals =	$943.81		$1,017.5622	$1,017.57	$1,017.55	$1,017.60