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	$67.25	4.269%	$70.1209	$70.12	$70.10	$70.10
Purchase #2	$77.99	6.129%	$82.77	$82.77	$82.75	$82.80
Purchase #3	$158.90	4.509%	$166.0648	$166.06	$166.05	$166.10
Purchase #4	$176.80	4.407%	$184.5916	$184.59	$184.60	$184.60
Purchase #5	$134.93	4.814%	$141.4255	$141.43	$141.45	$141.40
Purchase #6	$153.76	7.671%	$165.5549	$165.55	$165.55	$165.60
Purchase #7	$250.27	5.833%	$264.8682	$264.87	$264.85	$264.90
7 purchase totals =	$1,019.90		$1,075.3959	$1,075.39	$1,075.35	$1,075.50