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	$96.90	11.122%	$107.6772	$107.68	$107.70	$107.70
Purchase #2	$198.58	10.215%	$218.8649	$218.86	$218.85	$218.90
Purchase #3	$164.45	5.238%	$173.0639	$173.06	$173.05	$173.10
Purchase #4	$151.37	7.268%	$162.3716	$162.37	$162.35	$162.40
Purchase #5	$91.35	9.762%	$100.2676	$100.27	$100.25	$100.30
Purchase #6	$10.34	7.338%	$11.0987	$11.10	$11.10	$11.10
Purchase #7	$82.66	7.789%	$89.0984	$89.10	$89.10	$89.10
7 purchase totals =	$795.65		$862.4423	$862.44	$862.40	$862.60