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	$62.49	7.473%	$67.1599	$67.16	$67.15	$67.20
Purchase #2	$11.72	5.324%	$12.344	$12.34	$12.35	$12.30
Purchase #3	$189.64	4.671%	$198.4981	$198.50	$198.50	$198.50
Purchase #4	$18.76	9.280%	$20.5009	$20.50	$20.50	$20.50
Purchase #5	$100.61	4.635%	$105.2733	$105.27	$105.25	$105.30
Purchase #6	$62.92	7.149%	$67.4182	$67.42	$67.40	$67.40
Purchase #7	$172.88	12.133%	$193.8555	$193.86	$193.85	$193.90
7 purchase totals =	$619.02		$665.0499	$665.05	$665.00	$665.10