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	$103.49	7.314%	$111.0593	$111.06	$111.05	$111.10
Purchase #2	$166.78	7.832%	$179.8422	$179.84	$179.85	$179.80
Purchase #3	$171.39	8.205%	$185.4525	$185.45	$185.45	$185.50
Purchase #4	$12.68	9.685%	$13.9081	$13.91	$13.90	$13.90
Purchase #5	$57.98	10.715%	$64.1926	$64.19	$64.20	$64.20
Purchase #6	$159.31	13.635%	$181.0319	$181.03	$181.05	$181.00
Purchase #7	$54.95	13.461%	$62.3468	$62.35	$62.35	$62.30
7 purchase totals =	$726.58		$797.8334	$797.83	$797.85	$797.80