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	$79.68	3.248%	$82.268	$82.27	$82.25	$82.30
Purchase #2	$105.29	7.786%	$113.4879	$113.49	$113.50	$113.50
Purchase #3	$148.30	9.361%	$162.1824	$162.18	$162.20	$162.20
Purchase #4	$112.32	12.479%	$126.3364	$126.34	$126.35	$126.30
Purchase #5	$111.42	10.461%	$123.0756	$123.08	$123.10	$123.10
Purchase #6	$54.34	3.695%	$56.3479	$56.35	$56.35	$56.30
Purchase #7	$165.30	8.197%	$178.8496	$178.85	$178.85	$178.80
7 purchase totals =	$776.65		$842.5478	$842.56	$842.60	$842.50