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	$61.81	8.654%	$67.159	$67.16	$67.15	$67.20
Purchase #2	$111.43	9.544%	$122.0649	$122.06	$122.05	$122.10
Purchase #3	$239.29	12.555%	$269.3329	$269.33	$269.35	$269.30
Purchase #4	$204.32	10.740%	$226.264	$226.26	$226.25	$226.30
Purchase #5	$67.82	6.589%	$72.2887	$72.29	$72.30	$72.30
Purchase #6	$62.63	6.137%	$66.4736	$66.47	$66.45	$66.50
Purchase #7	$39.27	7.164%	$42.0833	$42.08	$42.10	$42.10
7 purchase totals =	$786.57		$865.6664	$865.65	$865.65	$865.80